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IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


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Nil 


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1.6 

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Photographic 

Sciences 
Corporation 


23  WEST  MAIN  STREET 

WEBSTER,  N.Y.  14580 

(716)  872-4503 


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CIHM/ICMH 

Microfiche 

Series. 


CIHM/ICMH 
Collection  de 
microfiches. 


Canadian  Institute  for  Historical  Microreproductions  /  Institut  Canadian  de  microreproductions  historiques 


Technical  and  Bibliographic  Notes/Notes  techniques  et  bibllographiques 


Tht/  institute  has  attempted  to  obtain  the  best 
o/lginal  copy  available  for  filming.  Features  of  this 
copy  which  may  be  bibliographically  unique, 
which  may  alter  any  of  the  Images  In  the 
reproduction,  or  which  may  significantly  change 
the  usual  method  of  filming,  are  checlced  below. 


L'Instltut  a  microfilm*  le  mellieur  exemplaire 
qu'ii  lui  a  *t*  possible  de  se  procurer.  Les  d6taiis 
de  cet  exemplaire  qui  sont  peut-Atre  uniques  du 
point  de  vue  bibiiographlque,  qui  peuvent  modifier 
une  image  reproduite,  ou  qui  peuvent  exiger  une 
raodification  dans  ia  methods  normaie  de  filmage 
sont  indiquis  ci-dessous. 


f-TT  Coloured  covers/ 
ALJ    Couverture  de  couleur 


D 


Covers  damaged/ 
Couverture  endommagAe 

Covers  restored  and/or  laminated/ 
Couverture  restaurie  et/ou  pelliculAe 

Cover  title  missing/ 

Le  titre  de  couverture  manque 


r— 1    Coloured  maps/ 


Cartes  giographiques  en  couleur 

Coloured  Ink  (i.e.  other  than  blue  or  blacit)/ 
Encre  de  couleur  (i.e.  autre  que  bieue  ou  noire) 


D 

□   Coloured  plates  and/or  Illustrations/ 
Planches  et/ou  illustrations  en  couleur 

□    Bound  with  other  material/ 
Rail*  avec  d'autres  documents 


D 


D 


D 


Tight  binding  may  cause  shadows  or  distortion 
along  interior  margin/ 

La  reiiure  serr6e  j;«ut  causer  de  i'ombre  ou  de  la 
distortion  ie  long  de  ia  marge  int«rieure 

Blank  leaves  added  during  restoration  may 
appear  within  the  text.  Whenever  possible,  these 
have  been  omitted  from  filming/ 
II  se  peut  que  certaines  pages  blanches  ajout6es 
lors  d'une  restauration  apparalssent  dans  le  texte, 
.  9is.  lorsque  ceia  Atait  possible,  ces  pages  n'ont 
pas  *t*  fiimAes. 

Additional  comments:/ 
Commentalres  supplAmentaires; 


□   Coloured  pages/ 
Pages  de  couleur 

□   Pages  damaged/ 
Pages  endommag6es 

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Pages  restauries  et/ou  peiilcui^es 


Pages  discoloured,  stained  or  foxed/ 
Pages  d*coior6es.  tachet6es  ou  piqudes 


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Transparence 

□    Quality  of  print  varies/ 
Qualit*  InAgale  de  I'impresslon 

□   Includes  supplementary  material/ 
Comprend  du  materiel  supplAmentaire 


D 
D 


Only  edition  available/ 
Seule  Edition  disponlble 

Pages  wholly  or  partially  obscured  by  errata 
slips,  tissues,  etc..  have  been  refiimed  to 
ensure  the  best  possible  image/ 
Les  pages  totaiement  ou  partieiiement 
obscurcles  par  un  feulllet  d'errata.  une  peiure, 
etc..  ont  «t«  filmies  A  nouveau  de  fagon  d 
obtenir  la  meiileure  image  possible. 


This  item  is  filmed  at  the  reduction  ratio  checked  below/ 
Ce  document  est  film*  au  taux  de  r*duction  indiqu*  ci-des«»ous. 

18X  22X 


10X 


14X 


12X 


16X 


20X 


26X 


30X 


24X 


28X 


3 


32X 


I 
ier 

9 

le 


The  copy  filmed  here  has  been  reproduced  thanks 
to  the  generosity  of: 

Library  of  Congress 
Photoduplicatlon  Service 

The  images  appearing  here  are  the  best  quality 
possible  considering  the  condition  and  legibility 
of  the  original  sopy  and  in  keeping  with  the 
filming  contract  specifications. 


Original  copies  in  printed  paper  covers  are  filmed 
beginning  with  the  front  cover  and  ending  on 
the  last  page  with  a  printed  or  illustrated  impres- 
sion, or  the  back  cover  when  appropriate.  All 
other  original  copies  are  filmed  beginning  on  the 
first  page  with  a  printed  or  illustrated  impres- 
sion, and  ending  on  the  last  page  with  a  printed 
or  illustrated  impression. 


The  last  recorded  frame  on  each  microfiche 
shall  contain  the  symbol  — ^>  (meaning  "CON- 
TINUED"), or  the  symbol  V  (meaning  "END"), 
whichever  applies. 

Maps,  plates,  charts,  etc.,  may  be  filmed  at 
different  reduction  ratios.  Those  too  large  to  be 
entirely  included  in  one  exposure  are  filmed 
beginning  in  the  upper  left  hand  corner,  left  to 
right  and  top  to  bottom,  as  many  frames  as 
required.  The  following  diagrams  illustrate  the 
method: 


L'exemplaire  filmA  fut  reproduit  grdce  d  la 
g6n«rositA  de: 

Library  of  Congress 
Photoduplicatlon  Service 

Lea  images  suivantes  ont  4tt6  reproduites  avec  le 
plus  grand  soln,  compte  tenu  de  la  condition  et 
de  la  nettat«  de  l'exemplaire  film6,  et  en 
conformity  avec  les  conditions  du  contrat  de 
fiimage. 

Les  exemplaires  originaux  dont  la  couverture  en 
papier  est  imprimAe  sont  film^s  en  commenpant 
par  le  premier  plat  et  en  terminant  soit  par  la 
dernidre  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration,  soit  par  le  second 
plat,  selon  le  cas.  Tous  les  autres  exemplaires 
originaux  sont  filmAs  en  commenqant  par  la 
premiere  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration  et  en  terminant  par 
la  dernidre  page  qui  comporte  une  telle 
empreinte. 

Un  des  symboies  suivants  apparaftra  sur  la 
dernidre  image  de  cheque  microfiche,  s>.  !on  le 
cas:  le  symbole  — ►  signifie  "A  SUIVRE ',  le 
symbole  V  signifie  "FIN". 

Les  cartes,  planches,  tableaux,  etc.,  peuvent  dtre 
film6s  d  des  taux  de  reduction  diff6rents. 
Lorsque  le  document  est  trop  grand  pour  dtre 
reproduit  en  un  seul  clichd,  11  est  film«  i  partir 
de  Tangle  supArieur  gauche,  de  gauche  d  droite, 
et  da  haut  en  bas,  en  prenant  le  nombre 
d'images  nAcessaire.  Les  diagrammes  suivants 
illustrent  la  mdthode. 


ate 


elure, 


H 


32X 


1 

2 

3 

1 

2 

3 

4 

5 

6 

j.*i».,-^-Mja'r 


If 


H 


'^ 


m 


?*^"i« 


i 


I 


Quartern'. 


Pliocene 


Miocene 


Loup  fork 
John  Day 
tthitrKi\ri 


Eocene 


Bridycr 
Purrco 


Crelactoui 


CeTacvans 


Jurasiic 


Triciisic 


Uppe 


crwiian 


Promammalici  'Ihcromorpha 


^aiiro-Alammalia. 


Hypotlii'tical  Phylot^euy  of  the  Xortli  .hiuriuin  Mamvialia. 

The  Monotremes  disappear  in  tlie  i.asal  llocene.  The  Marsupia's  ch.appear  in 
the  upper  Cretaceous  and  reappear  in  the  lower  Miocene  {Dhi.-l^hys).  The  aber- 
rant Placentals  branch  off  in  the  upper  Jurassic.  The  typical  I'lacentals  divide 
into  the  "Ancient  types  ••  dying  out  in  the  Miocene,  and  the  "Modern  types' 
still  existing.     The  aberrant  Placentals  are  given  off  in  niid-Mesozoic  times. 


i 


m 
de 


THE   RISE  OF  THE   MAMMALIA   IN  NORTH 

AMERICA. 

IIKNRV   FAIRFIKI.I)    OSIIORN. 

TWENTV  years  ago  an  era  opened  in  the  mammalian  palae- 
on  ology  of   Europe   and   America.     Partly   inspired    by  the 
Odontosraphie  of  Rutimeyer,  Kowalevsky  completed  and  pub- 
lished  in   1873  his  four  remarkable  memoirs  upon  the  hoofed 
mammals.    He  wrote  these  four  hundred  and  fifty  quarto  pa^es 
.n  three  languages  not  his  own.  in  French  upon  Anchitl!crUnn 
and  the  ancestry  of  the  horses,  in  English  upon  the  Ilyopo- 
tamtdac  m  German  xxvon  ^  siccus,  Anthracothcrinm  and  Entclo. 
don,  includmg  the  first  attempt  at  an  arrangement  of  a  great 
group   of   mammals    upon   the   basis   of  the  descent   theory 
These  memoirs  swept  aside  all  the  dry  traditional  fossil  lore 
of  Europe;  they  breathed  the  new  spirit  of  Darwin,  to  whom 
the  ch.ef  one  was  dedicated,  making  principles  of  descent  of 
more  importance  than  new  genera  and  species.     Kowalevsky 
thus  summed  up  the  contemporary  palaeontology: 

"After  the   splendid   osteological   investigations  of  Cuvier  had 
revealed  to  science  a  glimpse  of  a  new  mammalian  world  of  won- 
derful richness,  h.s  successors  have  been  bent  rather  upon  multi- 
pying  the  diversity  of  this  extinct  creation,   than  on   diligently 
studying  the  organization  of  the  fossil  forms  that  successively  turned 
up  under  the  zeal  of  amateurs  and  collectors.  .  .  .     With  the  excep- 
tion of  England  (referring  to  Owen,  Huxley,  Falconer,  and  others) 
where  the  study  of  fossil  mammalia  was  founded  on  a  sound  basis 
and  some  glorious  exceptions  on  the  continent  (referring  to  Ruti! 
meyer,  Gaudry,  Fraas,  Milne-Edwards),  we  have  very  few  good  palae- 
ontological  memoirs  in  which  the  osteology  of  extinct  mammals  has 
been  treated  with  sufficient  detail  and  discrimination;  and  thin^js 
have  come  to  such  a  pass,  that  we  know  far  better  the  osteology 
of  Sou  h  American  Australian,  and  Asiatic  genera  of  fossil  mammals 
than  of  those  found  in  Europe." 


Stud.  Biol.  Lab. 
Col.  Coll.,  I,  2. 


61 


--tn,iawws* 


J 


THE  RISE   OF  THE  MAMAfALIA 


At  the  same  time,  between  1871  and  1873,  the  pionfcers  of 
American  palaeontology,  Lcidy,  Marsh,  and  Cope  began  the 
exploration  of  our  ancient  lake  basins  rich  in  life.  The  first 
ten  years  of  their  work  not  only  revolutionized  our  ideas  of 
mammalian  descent,  but  brought  together  the  data  for  the 
generalizations  of  the  second  decade;  for  Marsh's  demonstra- 
tion of  the  laws  of  brain  evolution  in  relation  to  survival;  for 
Cope's  proof  of  ungulate  derivation  from  types  with  the  simple 
foot  resting  upon  the  sole,  and  with  the  conic  or  bunodont 
ancestral  molar  tooth;  and  finally  for  Cope's  demonstration 
of  the  tritubercular  molar  as  the  central  type  in  all  the  mam- 
malia. These  four  generalizations  furnished  a  new  working 
basis  for  morphology  and  phylogeny. 

In  these  twenty  years,  thanks  to  energetic  field  work,  we 
have  accumulated  vast  materials  for  the  history  of  the  rise 
of  th«  mammalia,  enough  for  ten  students  where  there  is  one, 
and  the  question  arises:  how  shall  we  take  best  advantage 
of  it,  what  methods  shall  we  adopt  ?  In  this  address,  besides 
bringing  before  you  the  more  recent  achievements  of  explora- 
tion and  research,  I  will  try  to  illustrate  the  advances  already 
made  in  lines  of  thought,  observation  and  system  in  palaeon- 
tology and  indicate  other  advances  which  seem  to  me  still 
desirable.  In  the  problem  of  how  to  think  and  work  most 
effectively,  and  with  most  permanent  results,  all  the  sciences 
meet  on  common  ground. 

Advances  in  Method. 

It  is  to  the  renown  of  the  veteran  Rutimeyer  and  of  Kowa- 
levsky,  so  soon  unfortunately  deceased,  that,  while  their  main 
inductions  suffer  by  American  discoveries,  their  methods  of 
thought  have  not  been  displaced.  It  matters  little  that  their 
theory,  that  ungulate  molars  sprang  from  lophodont  or  crested 
forms,  has  been  disproved;  that  Kowalevsky's  tables  of  descent 
are  full  of  errors ;  that  his  main  generalization  as  to  the  per- 
sistence of  adaptive  and  extinction  of  inadaptive  foot  types 
does  not  hold  good;  that  the  horses  and  Anchitherium  spring 
not  from  Palaeotherium  as  he  supposed,  but  from  Pachynolophus 


tN  NORTH  AMERICA. 


5 


' 


and  iryracotlicriuui,  types  which  he  carefully  studied  and  yet 
om.tted  from  the  horse  line!    It  is  the  right  system  of  thought 
which  IS  most  essential  to  progress;  better  in  the  end  wrong 
results  such  as  the  above,  reached  by  the  right  method,  than 
right   results   reached  hap-hazard  by  a  vicious  method      If  a 
student   asks  me  how  to  study  palaeontology,   I  can  do   no 
better  than  direct  him  to  the  Vcrsuch  cincrnatih lichen  Classi- 
ficatwH  dn-fossilcn  I luf thieve,  out  of  date  in  its  facts,  thor- 
oughly  modern  in  its  approach  to  ar.cient  nature.     This  work 
IS  a  rnodel  union  of  the  detailed  study  of  form  and  function 
with  theory  and  the  working  hypothesis.     It  regards  the  fossil 
not  as  a  petrified  skeleton,  but  as  moving  and  feeding;  every 
jomt  and  facet  has  a  meaning,  each  cusp  a  certain  significance 
Rising  to  the  philosophy  of  the  matter,  it  brings  the  mechanical 
perfection  and  adaptiveness  of  different  types  into  relation  with 
environment,  the  change  of  herbage,  the  introduction  of  grasses 
In  this  competition  it  speculates  upon  the  causes  of  the  rise 
spread  and  extinction  of  each  animal  group.     In  other  words' 
the  fossil  quadrupeds  arc  treated  biologically  ~^o  far  as  possible 
m  the  obscurity  of  the  past.     From  such  models  and  from  our 
own  experience  we  learn  to  feel  free  to  abandon  traditions  in 
the  use  of  the  tools  of  science,  such  as  mere  methods  of  descrfp. 
t.on  and  classification,  and  to  regard  priority  in  nomenclature 
only. 

New  discoveries  continually  produce  new  conditions  ;  there 
IS  nothmg  more  obstructive  than  the  reverence  for  old  ideas 
and  systems  which  have  outlived  their  usefulness.     In  obser- 
vation,  an  old  principle  was  do  minimis  mn  curat  lex;  now 
we  cannot  be  too  exact.     Every  cusp  and  facet  has  its  value' 
not  as  a  sign-post  for  a  new  species,  but  as  suggestive  of  some 
function  or  relationship.     Bird's-eye  methods  of  comparison, 
which,  for  example,  find  no  difference  between  a  rhinoceros 
and  a  loph.odon  molar,  a^  «  of  no  service  now  that  we  are 
called  upon  to  distinguish  between  so  m-ny  lines  of  ancient 
mammals  crowding  in  among  the  ancestors  of  existing  mam- 
mals.    Again,  palaeontology  is  not  a  science  apart ;  it  has 
always  gone  hand  in  hand  with  recent  osteology ;    it  must 
now  keep  abreast  with  the  embryology  of  the  teeth  and  skele- 

63 


a!'iu;iii;ujitwiaiugiiaj-_i^^i  iViijj  jij^i^^ 


ff 


6  THE  RISE  OF  THE  MAMMALIA 

ton-  with  the  animal  mechanics  of  Marey,  Allen,  and  Muy- 
bridge;    with   palaeobotany,   geology,    and   historical-physical 
geography.     In  these   points   we  cannot   be  too  broad.     All 
structures  should  be  considered  as  to  their  homologies,  their 
mechanics,  which  throw  such  a  brilliauL  ^icht  upon  their  evolu- 
tion- their  relations  to  the  food  and  soil,  and  to  other  parts. 
This'  brings  us  to  the  animal  as  a  whole  — its  tendencies,  its 
place  in  the  system  of  descent,  its  relations  to  its  contcmpo- 
raries,  the  causes  of  its  progression  or  retrogression  ;  finally, 
into  pure   speculation.      Here   I   am   reminded   of   a   critical 
saving  by  the  late  Professor  v.  Gudden,  the  distinguished  neu- 
rologist •  "Ein  Steinchen  der  Wahrheit  hat  mehr  Werth  als 
ein  grosser  Schwindclbau  "  ;  it  was  in  allusion  to  the  tempo- 
rary character  of  the  great  nerve-tract  systems  of  Meynert  and 
Flechsig      The  great  'Schwindclbau,'  literally  the  'disappear- 
ing  structure '    of   palaeontology,  is  the  phylctic  tree  which 
adorns  the  end  of  many  good  as  well  as  superficial  papers  ; 
and  recently,  because  of  its  extremely  brief  life,  has  fallen 
somewhat  into  disfavor.     I  do  not  think  the  present  reaction 
against  these  'trees'  is  a  wise  one  ;  we  must  remember  they 
are  the  working  hypotheses  of  our  branch  of  science  and  serve 
to  m.-st  clearly  express  present  knowledge. 

To  illustrate  some  of  these  principles  of  modern  methods, 
let  us  first  look  at  the  evolution  of  the  teeth  in  the  rise  of  the 
mammalia.  The  teeth  and  the  feet  are  the  foci  of  mammalian 
evolution,  the  only  direct  points  of  contact  with  food  and  the 
earth  Their  combined  use  in  phylogeny  has  increased  in 
interest,  because  their  evolution  has  proved  to  be  wholly^mde- 
pendent  We  recall  Cuvier's  famous  law,  of  which  Balzac 
said  at  the  time  :    "  Rebuilt  like  Cadmus  cities,  from  a  tooth. 

No  generalization  has  been  more  thoroughly  routed  than 
that  of  a  necessary  law  of  correlation  between  looth  and  foot 
structure  Besides  the  orthodox  clawed  carnivores  and  hooted 
pachyderms  of  the  t  eat  French  anatomist,  we  have  discovered 
hoofed  carnivores  such  as  Mesonyx.  and  clawed  pachyderms 
such  as  Chalicotherium.  Even  the  apparently  lastmg  barriers 
of  correlation,  which  Owen  raised  between  the  even  and  odd- 
toed  ungulates,  have  broken  down  by  Ameghino's  discovery  ol 

64 


AV  NORTH  AMERICA.  - 

a  Litoptern  odd-toed  horse  with  an  cvcn-toed  type  of  astra 
ga.us      Not  only  is  there  no  correlation  of  type,  but  none  in 
the  rate  of  evolution.     Hipparion.  the  most  projjressivc  horse 
in  tooth-structure,  probably  owed  its  extinction  to  its  cons-r 
vative   preservation    of   its   ancestral  three   toes.     For  thc^se 
reasons  the  teeth  and  feet,  owing  to  the  frequent  parallels  of 
adaptation,  may  wholly  mislead  us  if  taken  alone:  while    if 
considered  together,  they  give  us  a  sure  key  ;  for  no  case'  of 
exact  parallelism  in  both  teeth  and  feet  between  two  unrelated 
types  has  yet  been  found,  or  is  likely  to  be.     This,  I  believe  is 
the  one    esson  of  later  work  which  reverts  to  older  methods  • 
vve  should  not  base  either  classification  or  descent  upon  the 
teeth  or  feet  alone.     Every  additional  character  diminishes  the 
chances  of  error. 

The  evolution  of  foot  structure  has  now  become  a  science 
and  advances  have  been  made  in  the  principles  of  progression 
from  the  plantigrade,  pentadactyl  serial  types  to  ihe  un^ul,- 
grade,  monodactyl  alternating  types  which  are  of  the  greasiest 
.mpoitance  in  classification  and  phylogeny.      It  is  sufprising 
how   little   attention   was    given    to    ungulate   foot   str'ctur^ 
between  the  time  of  Cuvier  and  Kowalevsky.     Owen's  gener- 
alization as  to  the  Artiodactyland  Perissodactyl  pes  formed  the 
one  bright  exception.     Kowalevsky  first  directed  attention  to 
the  importance  of  the  more  median  metacarpals  displacing,  or 
spreading  to  gam  a  stronger  foothold  upon  the  earp!als  as  the 
lateral  toes  disappeared.     Ryder  also  worked  out  the  laws  of 
reduction.     The  discovery  of  Phenacodus  led  Cope  to  the  final 
generalization  that  the  primitive  ungulates  were  not  only  planti- 
grade but  had  some  of  their  carpals  and  tarsals  in  vertical  rows 
like  bricks  clumsily  set  with  unstruck  joints -and  that  one 
grea.  Lw  of  evolution  towards  digitigradism  was  to  produce 

itTed?  1      r"'"^  ^""''-     "-'  '^  ^^""^'  ^his  alternation 
differed  both  m  degree  and  kind  in  different  groups,  he  revived 

the  comprehensive   .Ungulate'   of  Linnaeus  and  divided  all 

great  0,27  ""'  "'°"  ''"'  ''''  ^'^"^^"^^  ^^^  «-« 

Rutimeyer  and  myself  have  shown  that  however  successful 

and  convenient  this  system  appears,  Cope's  lines  of  division 

65 


8 


THE  RISE  OF  THE  MAMMALIA 


ignore  the  fundamentally  different  modes  of  evolution  of  the 
fore  and  hind  feet;  an  animal  may  be  a  taxeopod  in  front  nnda 
diplarth  behind  or  vice  versa.  Numerous  exceptions  to  Cope's 
definitions  are  also  found.  The  discovery  of  the  aberrant 
ungulate  foot  types  of  South  America  further  invalidates  Cope's 
system  and  sustains  the  principle  that  to  be  permanent  classifi- 
cation must  be  based  upon  at  least  two  entirely  diverse  sets  of 
characters.  This  does  not  diminish  the  importance  of  the 
primitive  taxeopod  plantigrade  type  as  one  great  key  to  the 
still  unsolved  problems  of  the  primary  relationships  of  the  Con- 
dylarthra,  Hyracoidea,  Amblypoda,  Proboscidia,  Toxodontia, 
Litopterna,  Artiodactyla  and  Perissodactyla.  All  these  orders 
still  stand  apart  in  the  dim  past  like  so  many  mile-posts. 

While  Cope  overestimates  the  feet  in  these  larger  divisions/ 
many  writers  in  Europe  still  depend  wholly  upon  the  teeth  and 
ignore  the  wide  degrees  of  divergence  such  as  are  indicated  in 
the  Perissodactyla  for  example  in  functional  tetra-,  tri-  and  mono- 
dactylism.  By  '  functional '  we  refer  to  tendencies  which  a-e 
not  expressed  "in  the  bare  digital  formulas  — and  which  have 
the  same  relation  to  the  feet  that  the  dental  curve  h:.s  to  the 
teeth.  The  evolution  of  a  monodactyl  tendency  is  not  the 
work  of  a  century  but  of  a  geological  period,  a  principle  which  • 
we  wholly  ignore  when  we  place  the  monodactyl  Anehitheres 
with  the  tridactyl  Palaeotheres,  on  the  ground  that  the;r  dental 
type  and  digital  formulae  are  identical.  How  many  toes  an 
animal  has  is  of  far  less  importance  than  how  these  toe^^  are 
being  displaced  and  reduced. 

Lower  IViesozoic  Pro-Mammalia. 

With  the  exception  of  the  triassic  Theriodcsmus  of  Se^-lye, 
no  mammal  is  known  by  its  limbs  or  skeleton  unt"  we  reacn 
the  basal  Eocene  ;  in  studying  the  first  steps  in  the  rise  of  the 
mammalia,  we  are  thus  practically  driven  to  the  teeth  au-i 
jaws  alone.  In  these  straits  of  the  fossH-hunter,  embryology 
has  lately  come  famously  to  aid. 

Assuming  their  remote  reptilian  origin,  agreeing  with  Baur 
and  Kukenthal  that  the  theromorph  reptiles  were  parallel  with 

66 


IN  NORTH  AMERICA. 

rather  than  ancestral  to  the  mammals,  and  therefore  placing 
before  both  groups  the  hypothetical  Saurcmammals  in  or 
below  the  Permian,  we  come  to  the  old  question  which  Huxley 
discussed  m  his  famous  anniversary-address  :  "VVcs  there  a 
succession  between  Monotremes,  Marsupials,  and  Placcntals  or 
a  parallel  development  from  a  common  promammaiian  type'?" 
Then  we  look  to  the  newer  questions,  "When  were  the  Eden- 
tates  and  Cetaceans  given  off  ? " 

Modern  tooth-science  springs  first  from  the  recent  demon- 
stratioi^  of  Rutimeyer's  hypothesis  of  1869.  that  the  teeth  of 
a     the  mammals  centre  around  a  single  reptile-derived  type 
With  a  single  exception,  which  I  believe  can  be  disposed  of' 
various  stages  of  trituberculism  or  a  three-cusped  condition 
have  become  the  standard  for  the  teeth,  as  pentadactyly  has 
ong  been  for  the  feet,  except  that  this  is  developed  within 
the  mammalian  stem,   while  our  five  fingers  are  a  reptilian 
legacy.     Second,  it  springs  from  the  recent  thorough  explora- 
tion of  the  youngest  jaws  for  evidences  as  to  the  primitive 
form  and  s-iccession  of  the  teeth.     This  also   supports   the 
reptile  theory  of  tooth  descent  by  proving,  what  has  been  in 
considerable  doubt,  that  the  Promammalia  had  a  multiple  sue 
cession  of  teeth  like  the  reptiles,  and  that  even  some  of  the 
modern  mammals  retain  dim  traces  of  four  series  of  teeth 

The  brilliant  discoveries  of   Kukenthal.  Leche.   and  Rose 
begin  to  show  how  in  various  wa,s  the  mammals  early  modified 
the  regular  succession  of  all  the  teeth  by  suppression  of  parts 
of  the  multiple  series  ;  this  is  the  first  thing  to  consider     The 
next  is  how  heterodontism  arose,  how  the  conic  rows  of  teeth 
were  specialized  in  different  parts  of  the  jaw  for  three  or  four 
functions  ;  as  a  certain  number  of  teeth  took  up  each  function 
the  question  arises  whether  this  number  or  dental  formula  was 
ever  the  same  in  all  the  mammals,  for  we  know  it  is  very  differ 
ent  now.     After  the  teeth  were  thus  divided,  some  functions 
became   more  important  than  others,  and  established  a  mo- 
nopoly, causing  first  a  marked  difference  in  the  relative  develop 
ment  of  the  series,  which  we  may  express  in  a  dental  curve 
resulting  finally  in  a  loss  of  certain  teeth.     In  the  meantime      ' 
began  the  special  evolution  of  the  form  of  the  back  teeth,  or 

U7 


iiiffjfc  tfi 


I  i! 


lO 


THE  RISE  OF  THE  MAMMALIA 


molars.  Was  this  alike  in  all  mammals,  was  it  tritubercular  ? 
It  is  surprising  how  many  problems  of  early  lelationship  are  at 
stake  in  these  simple  processes. 

Primitive  Diphyodontism. 

What  does  succession  really  consist  in  ?     It  now  appears  that 
Baume  was  right  in  denying  that  the  first  tooth  is  the  mother 
of  the  second;  for  the  teeth  of  the  lower  as  well  as  the  upper 
series,  spring  from  the  common  epithelial  dental  fold  (Schmclz- 
leiste)  which  dips   down   from   the  surface  and  extends  the 
whole  length  of  the  jaw  ;  at  intervals  it  buds  off  the  dental 
caps  (Schmelzkcim)  of  the  first  series  ;  after  these  are  sepa- 
rated off,  the  dental  fold  sinks  and  buds  off  the  dental  caps  of 
the  second  series,  always  below  and  inside  the  first  ;  thus  the 
fold  is  the  mother  and  thr  caps  are  sisters,  twins,  or. triplets, 
according  to  the  number  of  the  series.     In  all  young  mammals, 
including  the  traditional  monophyodont  Cetaceans  and  Eden- 
tates,  and   excepting  only   the   still    unexplored   Monotreme 
embryos,  traces  of  two  series  of  teeth  have  been  found.    Both 
Leche  and  Rose  have  detected  evidence  that  the  dental  fold 
sometimes  buds  off  parts  of  a  third  series,  thus  explaining  the 
occasional  reversion  of  supernumerary  teeth  on  the  inner  side 
of  the  second  series,  and  Leche  has  seen  traces  of  budding 
preceding  the  first  series  — thus  giving  us  vestiges  of  four 

successions  ! 

All  our  perplexities  as  to  the  relations  of  the  milk  and 
permanent  teeth,  and  the  ingenious  but  mistaken  hypotheses  of 
Baume,  Flower,  Wortman,  and  Cope  have  sprung  from  our  want 
of  evidence  of  the  regular  and  complete  diphyodontism  of  the 
stem  mammals.  The  solution  in  brief  is  that  the  '  milk  teeth ' 
and  the  '  true  molars '  are  descended  from  the  first  series,  while 
the  second  series  is  represented  by  the  'permanent  incisors, 
canines,  and  pre-molars'  and  rudiments  of  dental  caps  beneath 
the  true  molars.  The  mammals  early  began  to  diverge  from 
this  primitive  diphyodontism  in  many  ways  ;  apparently  adapt- 
ing the  first  and  second  series,  respectively,  to  their  infant  and 
mature  feeding  habits;  losing  parts  oi  all  of  one  series  or  the 

68 


V-H„ 


•  IN  NOSTH  /l.UER/CA. 

olher.  and  in  some  cases  pushing  teeth  of  the  second  series  in 

In  the  Marsupials  (Kulcenthal)  almost  the  entire  first  series 
became  permanent  ;  thus  from  the  Jurassic  period  to  he 
present  t,me  only  a  solitary  fourth  premolar  ^f  the     eeond 

Observed  that  an  outer  upper-incisor  also  pushes  up  from  the 
second  ser,es  ;  the  remainder  of  the  second  series  sfil    pi,  ! 
as  r„d,me„.al  dental  caps  beneath  the  first,  even  b  nea'h   h' 
firs   and  second  molars  I    There  are  wide  variations  amo^  the 
Placentals  ;  thus  in  the  lowest  existing  forms,  the  Insectivora 
Leche  finds  that  in  the  Shrew  (&,r,)  the  second  serier    Z' 
pressed  entirely,  while  in   the  Hedgehog  iEn„aZ    of  . t 
twelve  permanent  teeth  in  the  anterior  part  of  the  jaws  five 
belong  to  the  first  series  and  seven  to  the  second.     We  thu 
meet  w,th  the  parado.,  that  among  the  .primitive'  Ma;supial 
and  Insecnvores  the  regular  reptilian  succession  was  early  in  e 

cession  of  two  senes  was  retained  in  the  anterior  part  of  the 

boTh  ^"'=='*/'"=  r'°*^  "igbly-specialized  molar    eeh„ 
both  Marsupials  and  Placentals,  the  second  teeth  were  ear'v 
suppressed  although  in  the  Edentates,  which  also  orTgira  ly 

teethTvf  I,"""""'  '"'"  '■'  "  '^Pi-^^'  =--»-on  of°seven 
teeth  behind  the  canine.  These  discoveries  prove  that  tte 
whale  teeth,  like  their  paddles,  have  acquired  as  coll 
adaptive  resemblance  to  those  of  the  Ichyosaurs.     Ho,"  dW 

'everot  aearl '7'^  f""  "'  '""  Edentates  and  Ce.aeea 
develop.'     Cleaily  by  retrogression.     As  Leche  points  out  in 
the  aquatic  Carnivora,  in  which  the  first  series  are  Segene^a  „ 
the    mgle-series  condition  (monophyodonti.=m)  advances  stc";; 
by  step  with   retrogressive   simplification  of    he  too  h  form 
(homodontism);  thus  in  the  true  seals,  the  eared  seals  and  th^ 
walruses,  as  the  permanent   teeth  become  simpl    ,  t,r  ml 
teeth  become  smaller.     The  Edentat<^<;    ^r.  ,„•  i  i 
genetically,  parallel  the  seals  i^tnt  '  t^.,  ^LTt,: 

the  same  time.     We  might  jump  to  the  conclusion  that  th^s 


12 


THE  RISE  OF  THE  MAMMALIA 


gives  us  an  explanation  of  the  homodont  and  apparently  mono- 
phyodont  condition  of  the  toothed  whales,  especially  as  it  has 
been  supposed  they  sprang  from  aquatic  Carnivora,  but  in  this 
Order  matters  were  reversed,  for  the  first  series  persisted  and 
the  second  series  were  suppressed  and  persist  as  a  rudimental 
row  of  tooth  caps  buried  in  the  jaw. 

Each  dental  series  has  an  adaptive  evolution  of  its  own,  in 
Erinaceus  the  first  scries  has  an  ancient  and  the  second  a 
modern  form;  in  Ericulus  both  series  are  alike;  in  the  Bats 
the  first  series  is  homodont  the  second  is  heterodont  (Leche); 
in  the  Edentates  the  first  series  is  ancient  and  heterodont  the 
second  is  modern  and  homodont  (Thomas,  Rheinhardt);  so 
among  the  Cetacea  and  Ungulata. 

What  deep  and  ancient  clefts  the  different  laws  of  succes- 
sion mark  between  the  Marsupials  and  these  three  Placental 
groups. 

Primitive  Heterodontism  and  Formula. 

Now  that  all  mammals  are  led  back  to  a  distant  diphyodont 
stem,  it  is  alsp  true  that  the  further  we  go  back  both  in  palin- 
genesis and  embryogenesis,  the  more  widespread  heterodont- 
ism is  —  all  modern  homodontism  proving  to  be  secondary. 
The  simple  conic  teeth  of  the  porpoise,  for  example,  bear 
a  misleading  resemblance  to  those  of  a  reptile.  Flower, 
Weber,  Julin,  and  KUkenthal  agree  that  the  ancestral  whales 
and  edentates  were  heterodont  and  had  a  smaller  number 
of   teeth  than  the  existing  forms. 

Heterodontism  is  then  the  second  problem.  When  did  the 
division  of  the  teeth  into  incisors,  premolars,  and  nolars 
occur,  before  or  after  the  Monotremes,  Marsupials,  and  Pla- 
cental separated  .>  It  is  well  settled  that  the  canine  was  the 
first  maxillary  tooth,  and  developed  from  the  most  anterior 
bi-fanged  premolar;  also,  from  the  discovery  of  complete 
succession,  we  must  now  define  the  first  molar  as  the  most 
anterior  specialized  or  triconid  tooth,  not  as  the  most  anterior 
permanent  tooth.  It  seems  to  me  we  now  find  strong  evidence 
that  the  stem  mammals  had  a  uniform  number  of  each  kind 

70  ' 


Himsr: 


'^fe.'Mfe'. 


IN  NORTH  AMERICA.  ,  - 

only  .0  prtaiUveTtcLot.    1"  r.^ft"'.  '°™^,  ■=<""' 
forward  when  „e  learn  whether  or  noMh     U.LT     ,"'" 

»  .ho  M„,.i.„bercu.are:  2  I      Tr'^^TT'"'  "=" 
Tritubcrculatc  teeth      rr,„.  i,  ,  "'"^  degenerate 

ceous   reeks   a     larkabT  Trt  h"™?' '"""'  '"  ""=  "^■'- 
TMacodon:    theTw  „rth.-,  T    ""'   '"^'"'^   *"-'  "™=» 

Mar.pia,; .  .rnrthtt  rthXL;:^::^!' T^'hT 

an  a  eharg  „T;  hS  ri"  •'  "  ,"'  ^'"'''"''ercu.ates'a"- 
they  were  poZfytt^^^l'^'^  ^™  "  "^^  l"-'  '•--< 
funetionally  akin  il  the  n  ^T  ,'  °"'',r"'"  ^■•""•'"lly  nor 

.he  MierohUrril' ';^~"  W^a7^'?"^"'  ""  '" 
and  a  eondvJe  evacHv  Mt„  .T.    ,  ^       ^  '''""'''  m«hanism 

trace  of  ^:x^^:^^:::,^^^  -'-v- 

Izn  pI  l}l\      ; .f'";'^'-  ^<^ntal  formula,   like   this^ 

Monotrc.es  had  a  ty;^,'^::;:'^^"*"'  ^^"^"^^^  ^°^^^'  '"^^ 

Our  next  step  is  to  unify  the  typic     c    ,    ,   .     r 
Marsupials  with  the  ?   i  a   /nfh.VK     i?     ^'       ^' '^  °^  ^'^'^^"^ 
shown    in    his  studie.  nf  5  7  ^^''''^'''^-     Thomas  has 

probablylost  onlr  hefo^toic  ,""''''f  ^'^^  '"^^^  ^^^ 
observation,  fortunately  is  n.  ^f^'^"' /''^"^"^^'-s  (//«•  2);  this 

an  embryo^ie  ^::^ ^"^Tl^:,^ t'' ' '""^ 
the  Jurassie  Marsupials.  Thomas  raised  th'^  ,'  '""'°''  '^ 
tral  incisors  to  five  tho  wT^  ^  """'''*'''  «^  '-inccs- 

Marsupials      Lse  therefo"  T""''  '"™  among  recent 

formity'  whin  he  shol^d    Lr?  :  M^^'"-  f  ^  '''"'''''  ""^-       ' 
a  member  of  the  second  s  n    '^'/.^"'".^"P'^'  ^S  is  probably 

be  reckoned  with     he  It       Nov      -T""'  "^'  ^^°"'^  ^^ 

Placentals    have  lo  t   one   in  '     ,  ""'  '''''^'''  ^'^^^ '  ^he 

lost   one   mcsor.  and   one   molar  abundant 

7t 


14 


THE  RISE  OF  THE  MAMMALIA 


evidence  of  which  is  found  in  Otocyon,  Centctes  and  Homo, 
we  derive  as  the  ancestral  formula  of  both  orders  : 

Incisors,  4  ;     Canines  and   Premolars,  5  ;     Molars,  4. 

The  aberrant  placental  Cetacea  point  in  the  same  direction 
as  we  read  in  the  conclusion  of  Weber's  fine  memoir:   "All 
the  Cetacea  sprang  from  a  stem  with  a  heterodont,  but  onlv 
partly  specialized  dentition  (something  like  that  of  Zeuglodon, 
3.  I.  p.  &  m  :  7),  .  .  .  not  direct  from  Carnivores  or  Ungulates, 
but  from  a  generalized  mammalian  type  of  the  Mesozoic  period, 
with  some  affinities  with  the  Carnivora.  .  .  .     Zeuglodon  itself 
branched  off  extremely  early  from  the  primitive  line,  and  the 
heterodont  Squalodon  (mark  its  formula,  3.  1.  4-  7-)  "branched 
off  later  from  the  toothed  whale  line,  after  the  teeth  had  begun 
to  increase  in  number  and  before  homodontism  had  set  in." 
It  would  be  easier  for  us  while  speculating  to  take  Squalodon 
and  the  Odontocetes  directly  from  the  Jurassic  mammalian 
formula  (3.  i.  4.  8.).    As  for  the  multiplication  of  this  formula, 
we  have  found  the  way,  says  Kiikenthal,  by  which  numerous 
homodont  teeth   have  arisen  from  a  few  heterodont  molars, 
it  is  by  the  splitting  up  of  the  numerous  triconid  molars  of 
Jurassic  ancestors  into  three.     He  substitutes  this  hypothesis 
for  the  one  advocated  by  Baume,  Julin,  Weber,  and  Winge, 
that  the  multiple  cetacean  teeth  represent  the  intercalation  or 
joint  appearance  of  both  the  first  and  second  series  of  teeth, 
owing  to  the  elongation  of  the  jaw  — a  view  which  is  now  dis- 
proved by  Kukenthal's  discovery  of  the  second  row  beneath 
the  first.     Since  even  by  Kiikenthal's  hypothesis  the  typical 
Mesozoic  mammals  could  not  furnish  as  many  teeth  as  are 
found  in  some  of  the  dolphins,  a  likelier  explanation  than  his 
seems  to  be  that  as  the  jaws  were  elongated  the  dental  fold 
was  carried  back  and  the  dental  caps  were  multiplied. 

The  Edentates,  like  the  Cetaceans,  point  back  to  hetcro- 
dontism,  and  somewhat  less  clearly  to  a  typical  dental  formula. 
We  are  here  indebted  to  Flower,  Rhcinhardt,  Thomas,  Kuken- 
thal,  and  Rose.  It  is  their  rudimental  and  useless  first  series 
which  gives  the  evidence  of  heterodontism.  while  the  second 

series   has  become   adaptively  rootless  and   homodont.     The 

especially  aberrant  feature  is  that  a  double  succession  exists 


\ 


7» 


I 


IN  NORTH  AMERICA.  ,- 

A.madUlo   presents    only    eight    maxillary    teeth,    seven    of 

^  ^  y  u   u  u  u  u  u  u  u  U--S 

-mmfmmmPT----' 

f  i^A^AT  vf/^^^  w -/ 

^'"""""  -'Z'^"  ^'''-^t  ''"J  Second  Series  of  Teeth 

which  are  preceded  by  two-rooted   milk  teeth  (Tomes)  ■   in 

he  embrjo  Leche  finds  fifteen  dental  caps,  of  whTch  '    v 

.h.rteen  are  calcified  ;  this  number  probably  include  the  Jot 

74 


I 


fl' 


mm 


i6 


THE  RISE   OF   THE  MAMMALIA 


rudimentary  incisors  observed  by  Rheinhardt.     In  the  aber- 
rant Orycteropus  (Aard-Vark),  witli  ten  adult  teeth,  Thomas 
finds  seven  milk  teeth  behind  the  maxillary  suture  (thus  takmg 
us  into  the  molar  region  of  the  typical  hcterodonts).     The  last 
of  these  milk  teeth  is  large,  and  two-rooted ;  behind  this  are 
three  large  permanent  posterior  teeth,  apparently  belonging  to 
the  first  series.     The  large  lateral  tooth  of  Bradypus  is  sug- 
gestive of  a  canine.      From  this   rapidly  accumulating  evi- 
dence  it  appears  probable  that  the  ancestral  Edentates  had  four 
incisors,  a  canine  and  eight  or  more  teeth  behind  it,  tie  double 
succession  extending  well  back  so  that  the  first  scries  did  not 
become  permanent  at  the  fifth  tooth,  behind  the  canme  as  m 
the  Marsupials  and  higher  Placentals.     If  these  are  primitive 
conditions,  as  seems   probable   from   comparison   with   fossil 
Edentates,  they  carry  the  divergence  of  the  Edentates,  like 
that  of  the  Cetaceans,  back  into  the  Mesozoic  period.     Com- 
parative anatomy  and  embryology  thus  point  back  to  highly 
varied  branches  of  a  generalized  placental  heterodont  stem  in 
the  Mesozoic,  and  a  much  earlier  divergence  than  we  formerly 
imagined.     Now  let  us  see  what  the  early  Mesozoic  mammals 

point  forward  to. 

There  are  three  distinct  and  contemporary  Jurassic  types, 
the  Multituberculates,   the  Triconodonts,   and  the  Trituber- 
culates      Are  -not  these  the  representatives  of  the  Protothena, 
Mctatheria,  and  Euthcria  ?     In  the  archaic  Multituberculates 
we  have  seen  a  monotreme  type  of  jaw  and  vestiges  of  a 
typical  ancestral  formula.     The  Triconodonts  are  a  newer 
group,   perhaps   derived   from  the  Dromotheriidac   (incipient 
Triconodonts)  of  the  Trias  although  these  appear  to  be  aber- 
rant ;  the  typical  forms  extend  from  Amphilcstes  to  Tricon- 
odon,   and  exhibit  the   first    stages   of    development  of   the 
inflected  Marsupial  jaw.    The  Trituberculates  include  the  Am- 
phitheriidae  and  Amblotheriidae  with  true  tuberculo-sectonal 
lower  molars,  like  those  of  modern  Insectivores  ;  they  alone 
exhibit  the  typical  angular  placental  jaw, -no  reason  can  be 
assigned  for  calling  them  Marsupials,  excepting  the  traditional 
reverence  for  the  Marsupial  stem  theory.     Now,  it  is  very 
significant  that  the  average  dentition  of  these  old  but  highly 


74 


T 


IN  NOKT/l  AMERrCA. 


'7 


<"iits,  4.   I.  4.  7..  TntubcTculatcs,  4.   ,.  ..    g.    j,  ^,„  ,,,„ 

malrit  diC"  "  '^^  """  ''"^  °'  """"^  """^  ■""  '"= 
Primilive  Trilubemilism. 

whole  f,,lK.s  and  reptiles  as  well  as  mammals,  ,„  f„,m  ,vlv,t 
are  ealled  ■  ,„c„„„d„n.  •  erowns  by  .he  a.ldi.ion  „,  la„.,..d  ct 
.0  s,mple  cones.     I„  the  mammals  alone,  these  ,„ree  e  sp 
pass  ,„t„  h.gher  stages  of  evolution,  through  what  t  cal  ed 
•tntuberculy;  in  whieh  these  eusps  form  a  trian;        ?he  d  ^ 
covery  of  pnmitive  wide-spread  tritubereuly  by  Cope    was  a 
great  step  forward.      In  looking  over  the  odonto,ra phiTof 
Cuv,e,  Owen,  Tomes  and  Banme,  we  find  there  is  no  .,  ,sp    ion 
of    h,s  eommon  type  around  whieh  the  highly  diverse  3 
n^aban  molars  een.re.     The  molars  of  the  elawcd  and  hoofrd 
mammals  ean  now  be  eompared,  as  „e  compare  the  h,,n,l  „ 
foot  of  the  bor,,e  ,vitb  that  of  the  ea*,  beeause  they  ,spri„™  „" 
a  eommon  type.    All  the  specialized  mammalian  series    uT 
gulates,  primates,  carnivores,  insectivores,  rodents,  marsupials' 
re  found  playmg  similar  yet  independent  adapti;e  varl'io t 

^.TT-  .'V""'  ""''  ""  '''y  '"  ""=  comparison  oal 
molars  w,h  each  other,  and  with  the  reptile  coL ;  take  the 
human  grmders  for  e.vample :  the  anterior  outer  euspri^  T. 
upper  jawaud  the  anterior  inner  cusps  in  th      o  3,:  Ire 
homologous   with   each   other  and   with    the   reptil    n    Jone 
Leavmg   as.de    for   the   moment   the   Multitube  en  le,   and 
Monotreraes,  every  known   triassie,   Jurassic,   cretae™,,     a^d 
basal  eocene  fossil  (excepting  Dicroeynodon)  is  in  some  sta^e 
of  trttubereuly  i  all  the  known  cretaceous  molars  are  simple 
.-.angles  above  ;  all  later  fossil  mammals  also  eonvere    o  .'f 
tubereuly     „,,  >    ,,,  f  eocene,  every  molar  is  tfi  u ta-    " 

lar,  and  the  early  stages  of  divergence  are  so  similar  that  it 

fZZt  Z     T'  '''  1°  '"■^""^'"»"  "-^  "°-  "f     ™-    oy 

Wf      .  '""■     ^"■'"yology  supports  the  evidence  of 

these  fosstl  ser.es  ;  thanks  .0  the  recent  admirable  researches 


,3  THE  RISE  or  THE  AfAAfAML/A 

of  Ruse  and  Tackcr.  wc  find  in  the  primates,  ungulates  ami 
marsupials,  that  every  molar  in  the  calcif.cat.on  of  ,ts  den  al 
caps  is  heraUlcd  by  f/<nr  cones  placed  ,n  a  tna„,h;  an.l  .n  the 
lower  jaw  these  three  cones  invariably  appear  in  the  same  order 
(protocnn.«.  paraeone  and  metacone)  in  which  they  arose  durm^ 
the  ren^oie  geological  periods. 

It  is  necessary  to  mention  this  overwhelming  palaeontologi- 
cal   evidence,   because   nrituberculy '    is  still  not   un.vers.-dly 
recognized;  Fleischmann  and  others  have  questioned  the  homo- 
ol"s  of  the  upper  and  lower  triangles,  and  two  able  writers. 
Rose  and  Forsyth  Major,  have  independently  proposed  an  op- 
Wion   theory   that   'multituborculy'  or  .polybuny'  ,s  the 
mammalian  archetype,  the  latter  author  believing  tntuberculy 
has  b-le  a  .dogria.'     So  far.  however,  from  there  bemg  any 
d    line  ""evidence.  I  am  now  able  to  add  the  Cretaceous  mam- 
malia to  the  tritubercular  lists  and  bring  forward  evidence  tha 
u'e  multitubercular  molar  instead  of  being  primitive  was  ckrived 
fom  the  tritubercular;  moreover,  all  the  researches  I  have 
bee^  quoting  tend  to  draw  the  mammals  without  exception  mto 
oSn?  three'  g.at  primary  forms.     The  ^apl^ont   orm  from 
which  Dromotherium  is  just  emerging  m  the  Trias,  is  the 
ddest  and  nearest  the  reptiles;  the  triconodont  or  three  cones 
^  1  ne  was  a  predominating  lower  Jurassic  type  ;  the  tntuber- 
cu  ir  or  three  cones  in  a  triangle  (trigonodont.  Rut.meyer  ,  was 
he  prevailing  upper  Jurassic  and  later  form.     The  fina    pre- 
dlhlce  of  the  tritubercular  over  the  others  was  due  to  Us 
possibilities  of  mechanical  adaptation  to  work  of  every  kind  - 
^r^Lfial  in  evolution.     Upon  the  VO^yV^y'^^-^^l^^^]': 
oricin  of  the  mammals  here  advocated,  we  must  adm  t,  first, 
he  independent  evolution  of  trituberculy  in  different  phy  a 
and  second,  the  branching  off  of  several  great  groups  m  the 
nre-tritubercular  stages.  ,    •.  ^i    ^  „„  f« 

^  In  the  problem  of  precedence  of  type.  I  admit  that  as  to 
an  iquity  there  is  nothing  to  choose.     The  contemporaneity  o 
h    R  letic  Microlestes  (a  plagiaulacid  Multitubercu  a  e  and 
the  upper  Triassic  Dromotherium  (an  early  Tntuberculate)  is  a 
puS  circumstance  ;  for,  by  my  hypothesis.  Microlestes  was 


i*#*« 


/x  .voA'r//  .i.u/:a'/c.i. 


'9 


even  at  that  time  sp.ciali/in;;  Iron,  .,  ,„.,rc  pri.nitivc  T.ituhcr- 
dilate  ancestor.     The  molar  ol    this  liitio  animal   is  a  narrow 
I'^MUituhereular    basin,    not    unlike    that    of    several    existing' 
nnicnts   wh.eh   are  ot   un.louhte.l   tritiihnenlar  ori..in  •   -.n.!   it 
•s  amon-   the  rodents  we   tind   the  explanation  ..rthc    Multi- 
tuherculate   moL.r.     The  molars  of  the  mouse  (Mt.s).  an.l  of 
certain    kanj^aroo    rats    (Dipo.lomys   an.l    IVro.,M,alhus).    illus- 
trate   heantifnlly   the   recent   stages   between  trituberculy  an.I 
mult.tubereuly.    showin^^    that    the    Interme.liate    tubercles    of 
Mils  (also  c.mmon    in  other  j.laeentals)  j;ivc  rise  to  the  inter- 
mediate  or   third    Multitubeivulate    row.'      I'hcn   each    row  is 
fortified  by  additional  tubercles  ;  so  that,  finally.  Peroj^nathus 
with    ,ts    lonj^itudinal    rows   of    cusps   and   ^^rooves.    is    in    ■[ 
.s.m.hvr  sta^^e  of   evolution   to  Tritylodun   of  the   upper  Trias 
of  South  Atnca.      This  proves  that  //..  /;v/;./v/vv.A,r  ;.../,,;-  /on- 
tlicpotcnUal  of  „  typi,,,i  ,n„liitulH;rulm:     Add  to  this  the  fact 
that   the   premolars   of   many   Mnltituberculates  (Ctenacodon. 
noh.don.  Chirox.)  are  tritubercular.  and  we  have  strong  indi- 
rect evidence   that    the   Mnltituberculates   had   Trituberculate 
ancestors.      As  for   Rose's   fusion    theory  of   Multituberculate 
oriK.n    It  may  be  pointed  out  that  the  oldest  types,  with  an 
abundance  of  primitive  reptilian  cones  to  fuse,  have  only  five 
or  SIX  cusps,  while  the  newest  types,  remote  from  the  reptiles 
have  a,s  many  as  twenty-five  cusps.     Fleischmann's  objection 
IS  of  a  different  character  ;   he  believes,  from  his  studies  of  the 
Insectivora.  that  Cope  and  myself   have  mistaken  the  homo- 
logies of  the  parts  in  the  upper  and  lower  molars,  and  endea- 
vors to  show  that  the  posterior  end  (talon)  of  the  lower  molar 
^equivalent  to  the  anterior  end  (trigon)  of  the  upper  molar 
His  position  is  shown  untenable  by  a  study  of  Spalacotherium' 
and  other  Jurassic  types  in  which  there  is  no  talon  below  or 
above,  and  it  is  proved  that  the  upper  and  lower  trij^ons  must 
be   homologous.     The   teeth   of  this   form    should   also   settle 
Roses  doubts  as  to  the  position  of  the  reptilian  protocone  in 
trie  upper  and  lower  jaws. 

E.xaminc  evidence  of  another  kind  as  to  the  primitive  tvpe 
Retrogression  inverts  the  order  of  evolution.     We  know 'this 

>  Prof.  J.  .A.  .Allen  and  Dr.  J.  L.  Wortman  kindly  as.sisted  me  in  this  comparison. 


20  THE  RISE  OF  THE  MAMMALIA 

Of  Thylacinns,  in  which  a  tritubercular  molar  turns  back 
into  a  triconodont.  In  the  aquatic  Carnivora,  the  seals,  eared 
seals  nnd  walruses,  the  triconodont  is  also  retrogressing  into 
the  haplodont.  The  inference  is  a  fair  one  that  the  aquatic, 
like  the  terrestrial  Carnivora.  were  originally  tntubercular. 
With  the  Cetace.  both  palaeontolo-y  and  embryology  take  ur, 
back  to  a  more  or  less  typical  triconodorc  molar,  not  to  the 
tritubercular.  The  Edentates  also  giv.  feebler  evidence  of 
ancestral  triconodont  or  tritubercular  molar  forms 

Thus,  the  tendency  of  late  research  is  to  show  that  all 
stem  mammals  were  related  in  their"  double  succession  in 
their  dental  formula,  and  in  their  primitive  molar  form.  These 
features  point,  not  to  a  succession,  but  to  a  unity  of  ancestry 
of  the  Monotrtmes,  Marsupials,  and  Placentals. 


Divergence  of  the  three  Groups. 
The  discovery  of  the  complete  double  series  seems  to  have 
removed   the   last   straw  from   the   theory  of   the  Marsupial 
ancestry  of  the  placentals.  for  the  peculiar  mode  of  suppres- 
sion of  the  second  series  in  the  Marsupials  has  been  constan 
since  the  Purbeck  ;  this  difficulty  is  added  to  the  structure  o 
the  iaw,  the  epipubic  bones,  the  profoundly  different  mode  of 
foetal  nutrition.     None  the  less,  any  conclusion  we  can  dravv 
now  as  to  the  primary  relations  of  the  three  great  groups  is 
more  or  les.  of  a  •  Schwindelbau,'  and  I  put  together  the 
resnits  of  these  later  discoveries  with  a  full  realization  of  the 
temporary  character  of  present  conclusions. 

The  Permian  Sauro-Mammalia  (Baur)  with  a  multiple  suc- 
cession of  simple  conical  teeth  divided  into  :  A.  Theromorpha. 
which  lost  the  succession  and  in  some  linos  acquired  a  hetero- 
dont  dentition  and   triconid   single-fanged   molars  ;     B,    Pro- 

"^ThThypothetical  lower  Triassic  Promammalia  retained   a 
double  secession  of  the  teeth  ;  they  became  heterodont,  with  , 
incipient  triconid  double-fanged  molars  ;  dental  formula  approx- 
imating 4.  1.4-5.8.     They   gave  rise   to    ciu^e   groups:     I.^ 
The  Pfototheria  which  passed  rapidly  through  che  tritubercular 

78 


IN  NORTH  AMERICA.  j, 

into  the  multitubercular  molars  in  the  line  of  Multituberculates, 
and  more  slowly  into  tritubcrculy  and  its  later  stages  in  the 
hne  of  Monotremes.     li.  The  Metatiicria  or  Marsupials  tended 
to   suppress    the   second  series  of  teeth,  except  those  inter- 
calated with  the  first  ;   by  this  and  by  reduction  the  formula 
became  5.  1.3.  4-6  ;  the  molars  passed  slowly  throu-h  the  tri- 
conodont  into  the  typical  tritubercular  type.    III.   The  Eutheria 
or  Placentals  divided  early  into  a  number  of  branches,  in  which 
there  was  heterodontism,  but  no  uniform  modification  of  succes- 
sion, namely:    A,  forms  suppressing  the  second  scries  in  the 
molar  region  only,  and  acquiring  a  typical  Eulherian  dentition, 
3.1.4-  3-4-      I.  The  Insectivores  tended  to  partly  suppress  the 
anterior  teeth  of  the  second  series  or  intercalate  them  with 
teeth  of  the  first  series  ;    the  molars  became  tritubercular.     2 
The  higher  Placentals  retained  the  succession  of  tlic  first  and 
second  series  as  far  back  as  the  first  mola,r  ;  the  molars  entered 
rapidly  into  tritubcrculy  aiul  ils  higlier  stages.     13,  forms  retain-    . 
ing  the  double  succession  in  part  of  the  molar  region,  and 
retaining  more  of  the  primitive  dentition,  4.  i.  4.  8      3    The 
Edentates  branched  off  from   an  early  triconodont  or  "tritu- 
bercular diphyodont  stage,  with  numerous  molars,  and  second- 
arily  suppressed  the  first   heterodont  series,  and  established 
a  numerous  homodont   second  series.      4,    The  Cetacea  also 
branched  off  from  a  diphyodont,  heterodont  stage,  and  second- 
arily established  a  numerous  homodont  first   series,  and  sup- 
pressed the  second  series. 


Origin  and  Evolution  of  TRiTUKERcuLisri. 
'Concrescence'  is  the  newest  theory  of  cusp  solution  — 
an  expansion  by  Kukenthal  and  Rose  of  views  eadier  e.x 
pressed  by  Gaudry,  Magitot  and  Dybowski.  As  Kukenthal 
derives  three  conical  Cetacean  teeth  by  splitting  apart  a 
triconodont  molar,  he  conversely  derives  a  triconodont  molar 
by  bringing  together  of  three  reptile  cones.  Smith  Wood- 
ward  has  called  attention  to  the  support  the  epidermal 
structures  of  the  fishes  give  to  this  hypothesis,  yet  as  applied 
to  mammalian  teeth,  it  comes  from  a  one-sided  Morphology 


22  THE  RISE  OF  THE  MAMMALIA 

which  regards  only  the  wonderful  though  mutilated  chapters 
of  Embryology  when  the  untorn  pages  of  palaeontology  are 
at  hand.     Between  the  Trias  and  the  Puerco,  we  are,  so  to 
speak,  ill  at  the  birth  of  every  successive  cusp,  and  can  observe 
positively  that  the  law  of  cusp  evolution  is  direct  upcro-vth 
from  the  smooth  slopes  of  the  crown  or  from  the  cmgulun^ 
that  fertile  parent  of  new  cusps.     Each  new  cusp  is  usually 
preceded    by    an    abraded    surface,    and    prophesied    by    an 
excessively  minute  hillock.     It  follows  from  this  that  cusps 
ran-e  in  size  and   height  directly  according  to  their  age  — 
a  principle  beautifully  demonstrated  in  some  of  the  Mesozoic 
teeth      If  the  Kiikenthal-Rose  theory  were  correct,  the  oldest 
triconodonts  should  be  iso-conid,  whereas  we  know  that  the 
three  equal  cones  of  Triconodon  arc  all  a  very  late  develop- 
ment ;    the  earlier  forms  show  the  lateral  cones  receding  to 
the  needle-points  of    Dromotherium.  _ 

The  tritubercular  molar  owes  its   survival  to  the  onginal 
advanta-c  of  its  triangular  form,  and  to  the  possibilities  of  free 
cusp  addition -as  worked  out  by  Cope.  Wortman,  Schlosscr, 
Scott    and   myself.      Riitimeyer's    term,    'trigonodont,'    best 
expresses   the    primitive   structure   of    the   upper   and -lower 
teeth   as  of  two  interlocking  triangles  with  their  open  bases 
turned  outward  in  the  upper  and  inward  in  the  lower   jaw. 
These    'trigons,'    cutting   past  each   other,  made  a  shear  so 
perfect    that   many    Inscct.vora   retained   it   without   further 
evolution.      But    in   most   Trituberculatcs  a  talon  was   next 
added  to  the  lower  molar  (Jurassic  stage)  as  a  pestle  crushing 
into   the   upper  valley  ;    this  talon  gradually  widened  mto  a 
broad  heel  supporting  three  cusps,  as  found  in  the  Cretaceous. 
Consider    the    extreme   antiquity   of    the    three    homologous 
cusps    borne    upon    the    back    part    of    the    human    molar. 
Th's  addition   gave    the  opposed  molars  two  shears  and  one 
crusher,  and  was  so  perfectly  adapted  to  tlie  needs  oi  Lemurs 
and   many    Insectivores   and   Carnivores,    in   short,    of    most 
clawed   animals,  that    they    stopped    at   this    point.     Not    so 
with  the  Ilerbivora,  which  required  more  extensive  crushing 
surfaces      The  upper  molars,  which  had  remained  triangular 
throuo-h  the  Cretaceous  and  into  the  basal  Eocene,  began  to 


IN  NORTH  AMERICA. 


n 


chapters 
ilogy  are 
re,  so  to 
\  observe 
ipjjro'Vth 
ingulun\ 
is  usually 
1    by    an 
lat  cusps 
iir  age  — 
Mcsozoic 
:hc  oldest 
that  the 
;  develop- 
ceding  to 

e  original 
ies  of  free 
Schlosscr, 
)nt,'  best 
ind  •  lower 
pen  bases 
^wer   jaw. 

shear  so 
.it   further 
was    next 
e  crushing 
led  into  a 
Cetaceous, 
omologous 
an    molar, 
■s  and  one 
of  Lemurs 
,    of    most 
.     Not    so 
e  crushing 

triangular 
?,  began  to 


develop  a  little  talon,  like  that  early  seen  in  the  lower  molars 
and  at  the  same  time  both  upper  and  lower  molars  entirely 
sacrificed  their  primitive  cutting  powers,  and  were  converted 
from  secodont  into  bunodont  types  by  bringing  the  primitive 


*o*o»o' 


o-O-oo-O-o 


B 


D 


<K>>  «>0>   K>o 


VAVAV 


'^Ml^r^-'^MM 


I 


J 


Phylctk  nutory  of  Ihe  CusJ-s  of  the  U,tgutate  Mo!urs. 


Trhi  r  T  '  '  "^P'°J^°"''  f  ^^'"'^''-  ^'  P^°todont  Stage  KDrc.otlurium), 
7  assjc.  r  rr^onodont  Stage  i^AmphiUstes).  D,  Tritubercular  Stage  (SpaU- 
cothertum)  ^.  1  ntubercular-tuberculo  Sectorial,  Lower  Jurassic.  /;  The  sZe 
m  Upper  Jurassic.  G,  The  same.  i„  Upper  Cretaceous.  //.  The  s^I.  Pue^o 
Louxr  Locene.  /,  .Vxitubercular-sexitubercular,  Puerco.  /.  SeSubercular- 
quadntubercular,  Wahsatch.  ^    ^exituoercular- 

trigons  down  to  the  level  of  the  talons.     At  the  same  time 
the   upper   molars   acquired   intermediate   tubercles,  and  the 
triangular  or  oblique  arrangement  of  the  tubercles  was  shifted 
into  the  quadrangular  or  transverse  arrangement.     This  out 
Ime  IS  the  result  of  fifteen  years'  observation. 

8i 


24 


THE  RISE  OF  THE  MAMMALIA 


With  square  crowns  {vs.  triangular)  and  six  conic  cusps 
above  and  below  the  molars  of  the  Artiodactyl  and  Perisso- 
dactyl  Herbivora  ended  their  first  constructive  period  at  that 
period,  and  started  upon  their  modernization.  From  this 
point  wc  dnect  our  attention  upon  the  numerous  combinations 
of  three  or  four  forms  assumed  by  these  single  cones.  The 
important  thing  now  is  to  determine  at  what  period  these 
combinations  were  established,  for  there  is  wide  difference 
of  opinion  as  to  when  ungulate  divergence  began.  To  this 
I  refcT  later.  Taeker  has  recently  shown  how  every  modern 
embryonic  lophodont  or  selenodont  molar  first  exhibits  the 
archetypal  cones  of  the  primitive  bunodont.  This  law, 
together  with  my  own  parallel  stu.lics  of  the  evolution  of  the 


A  B 

The  Limits  of  VariaAon. 

A,  Merychipfus.     B,  Acemtherlum.      Showing  the  secondary  enamel  fokUnss 
of  the  crests  arising  from  the  centres  of  the  ancestral  cones. 

horse  and  rhinoceros  molars,  led  me  to  the  discovery  that  these 
cmbrvonic  primitive  cones  are  also  the  main  growth  centers, 
for,  in  the  upper  Miocene,  long  after  the  perissoda^iyla  have 
separated  from  each  other,  wc  see  the  influence  of  the  arche- 
typal form  in  the  generic  and  specific  variations  of  the 
molars.  Compare  the  teeth  of  Mcrychippus  and  of  Accrathc- 
rium,  and  imagine  that  you  see  underlying  the  diverse  crests 
and  crescents  the  simple  bunodont  molar  of  such  a  form  as 
Hyraeotherium  leporinum  of  the  London  Clay.  You  will 
then  notice  that  the  characteristic  secondary  folds  and  spurs 
of  the  Miocene  teeth  spring  from  the  old  bunodont  cones,  that 
the  tv'o  '  cement  lakes '  of  Merychippus  are  equivalent  to  the 
two    'fossettes'    of    Aceratherium,   because   the    'crcscentic 


LV  NORTH  AMERICA. 


25 


spurs'  of  the  horse  and  the  'crochet'  and  'antccrochet '  of 
the  rhinoceros  spring  alike  from  the  primitive  'intermediate 
tubercles.' 

In  view  of  these  discoveries  of  the  uniformity  of  mam- 
malian molar  type,  a  uniform  terminology  has'  become  as 
necessary  for  the  dental  cusps  as  for  the  carpal  and  tarsal 
elements  of  the  feet.  Professor  Gaudry's  once  admirable 
system,  elaborated  in  his  ' Enc/mincmaits,'  was  based  upon  the 
sufjposcd  division  of  the  ungulate  molar  into  the  'first  lobe' 
and  'second  lobe,'  and  is  still  followed  in  France.  Yet  it  has 
two  drawbacks  :  it  precludes  the  comparison  of  the  ungulate 
with  the  unguiculate  molar,  for  neither  lobe  includes  the 
complete  triangle  ;  still  more  inconvenient  is  the  fact  that  we 
cannot  compare  the  higher  ungulates  with  the  older  Cory- 
phodons  and  Pcriptychidac  in  which  the  molars  were  developed 
upon  the  triangular  plan  ;  these  teeth  have  only  the  first 
lobe  and  half  the  second.  The  upper  molars  of  Hipparion 
and  Coryphodon  illustrate  the  advantages  of  this  new  system 
of  comparison  and  of  terminology. 

Scott  has  made  a  further  advance  in  Odontology  by  working- 
out  the  laws  of  premolar  evolution  or  cusp  addition.     In  many 
groups  we  know  that  from  one  to  four  of  the  premolars  grad- 
ually acquire  the  exact  form  of  the  molars  in  order  to  further 
increase  the  grinding  surface,  and  we  should  a  priori  expect 
that  the  cusps  would  be  added  in  the  same  order,  and  therefore 
be  homologous  with  the  molars.     This,  as  Schlosser  and  myself 
had  observed,  is  not  the  case.     Scott  shows  the  order  of  cusp 
development  in  the  premolars  is  very  nearly  the  same  in  all  the 
mammals,  and  yet  is  entirely  different  from  the  order  followed 
in  the  molars.     This  law  again  unexpectedly  ties  the  clawed 
and   hoofed   mammals    together;   the   sequence   of    cusps    in 
palingenesis  is  smiilar  to  that  observed  by  Taeker  in  embryo- 
genesis,  and  Scott  is  justified  in  proposing  a  new  terminology 
(protoeone,    deuterocone,    trittocone,    etc.)   for   the    premolar 
cusps,  which  will  in  the  end  prove  to  be  a  great  convenience. 
I  alluded  above  to  the  well-known  extreme  and  very  confus- 
ing similarity  of  the  tritubercular  molars  in  the  early  stages  of 
Trituberculism  is  at  once  the  cause  of  clearness 
83 


divergence 


26 


THE  RISE  OF  THE  MAMMALIA 


and  of  doubt  when  we  get  back  to  the  stem  mammals  of  wiicly 
different  phyla.  This  has  led  to  strange  misconceptions  of 
phyletic  affinities  as  exemplified  in  Filhol's  division  <  Pachy- 
Ihnuricns^  q.  supposed  mixture  of  lemur  and  ungulate  stock. 
There  was  never  any  such  mixture,  and  the  question  comes  up 
how  to  distinguish  unlike  forms  with  like  teeth  ?  I  have  pro- 
posed to  make  use  of  a  dental  cun'c  which  will  express  the 
incipient  atrophy  of  some  parts,  and  hypertrophy  of  other  parts 
of  the  series,  a  metatrophism  which  will  naturally  terminate 
in  the  reduction  of  some  teeth,  and  excessive  development  of 
others.  This  has  not  been  by  any  means  fully  worked  out,  but 
I  believe  it  will  prove  to  be  of  great  service  in  directing  atten- 
tion to  some  of  the  initial  tendencies  of  divergence,  which  are 
not  expressed  either  in  the  dental  formula  or  in  the  patterns  of 
the  teeth.     Below  are  some  of  these  curves.     When  worked 


Homodont 


Jurassic  Insectivora 


L>emurs 


Monkeys 


Modern  Carnivores 

I  i  t 

'      /       '    C    '  P 

Examples  of  Dental  Curves. 

out  by  the  composite  method,  we  will  find  certain  primary 
curves  characteristic  of  the  ordinal  divisions,  and  minor  curves 
distinguishing  the  lesser  divisions.  Of  course  the  laws  of 
parallelism  will  also  be  found  in  force  here  ;  flesh-eating,  insect- 
eating,  and  grass-eating  animals  will  be  apt  to  have  similar 
curves  even  when  evolved  in  different  groups,  but  here  the 

dental  formula  and  succession  will  come  to  our  aid. 

84 


L 


IN  NORTH  AMERICA. 


a; 


Breaks  and  Links  in  the  Mesozoic  Fauna, 
By  our  hypothesis  all  three  sub-classes  flourished  together 
during  the  American  Mesozoic;  the  Marsupials  disappeared, 
then  the  Monotremes,  and  by  the  end  of  the  basal  Eocene  the 
Placentals  were  in  exclusive  possession  of  the  northern  con- 
tinent. 

Although  we  have  great  reason  to  congratulate  ourselves 
upon  the  rapid  progress  of  discovery,  there  still  remain  great 
gaps  in  Mesozoic  time  between  certain  horizons  and  in  the  lineal 
phyletic  series  of  both  the  Mesozoic  and  Cenozoic.  For  a 
time  standard  we  may  take  advantage  of  the  remarkably  con- 
stant evolution  of  the  Plagiaulacidae  in  the  Mesozoic,  and  of 
the  Equidae  in  the  Cenozoic  — as  certain  invertebrates  are 
made  use  of  in  older  rocks.  The  grooves  and  tubercles  of 
Plagiaulax  and  the  cusps  and  styles  of  the  horses  are  added 
with  Uie  precision  of  clockwork,  and  supposing  that  the  rate  of 
evolution  has  been  about  the  same,  we  can  approximately 
estimate  both  the  periods  of  deposition  and  the  intervals  as 
below. 

plagiaulacidae. 

^T       u         r   „  ,  Stonesfield.    Purbeck.    Laramie.    Puerco.    Cernaysua. 

Number  of  Premolars,  ?  4,3  2  2-1  i 

Grooves  on  Premolars,  ?  -j^       i,.,^     ,2_,^      j^ 

Molar  Tubercles:  outer ;  inner ;      ?  4:2        6:4        6:4       9:6 

Estimating  the  geological  intervals  by  dental  evolution  and 
fauiial  succession,  there  is  first  the  great  gap  between  the 
Trias  of  Microlestes  and  Dromotherium  and  the  Jurassic  of 
the  Stonesfield  slate  ;  there  is  a  relatively  shorter  interval,  but 
still  a  considerable  one  between  this  and  the  Purbeck  or  Atlan- 
tosaurus  beds.  Then  follows  another  long  and  very  important 
interval  between  the  Atlantosaurus  beds  and  the  Laramie 
(Upper  Cretaceous).  The  gap  between  the  Laramie  and 
Puerco  was  relatively  short  as  indicated  by  the  comparatively 
limiteJ  evolution  both  of  the  Plagiaulacids  and  Trituberculates. 
The  Puerco  itself  was  a  long  period  in  which  the  Plagiaulacids 
underwent   considerable   changes.     Then  follows  an   interval 

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28 


ThE   RISE  OF  THE  MAMAfALIA 


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/A-  NORTH  AMERICA. 


49 


which  it  is  most  important  to  fill  by  future  exploration,  for 
between  the  Puerco  and  th<'  Wahsatch  the  differentiation  of 
the  even  an^J  the  odd-toed  ungulates  must  have  occurred.  The 
Wahsatch  proper  does  not  mark  a  very  extensive  evolution  of 
the  forms  it  contains.  It  passes  after  a  slight  break  into  the 
base  of  the  Bridger  (Wind  River)  and  then  begins  that  splendid 
and  almost  uninterrupted  succession  of  lake  basin.s,  terminat- 
ing in  the  pliocene.  I  append  a  Table,  to  be  compared  with 
that  published  by  Marsh  in  his  admirable  address  of  1877,  and 
exhibit  the  great  progress  of  the  last  si.\teen  years. 

The  general  faunal  succession  is  marked  by  the  sudden 
appcarancj  and  disappearance  of  certain  series  and  rise  and 
fall  of  great  groups.  In  the  Trias  appears  the  remarkable  pro- 
todont  or  primitive-toothed  Dromothcrium;  wc  cannot  deter- 
mine its  Order  at  present.  We  still  have  no  American  fauna 
corresponding  to  the  intermediate  Stonesfield  01  England.  In 
the  Jurassic  Atlantosaurus  beds  the  three  supposed  repre- 
sentatives of  the  Monotremes  (multituberculatcs),  Marsupials 
(triconodonts)  and  Placentals  (trituberculates),  appear  in  equal 
numbers;  the  latter  are  generally  characterized  by  the  primitive 
dental  formula.  In  the  Laramie  the  Multituberculatcs  continue 
in  great  profusion,  and  the  Marsupials  and  Placentals  are  also 
numerous. 

The  serial  succession  of  the  Trituberculates  from  the  Meso- 
zoic  is  still  an  unknown  chapter;  we  are  utterly  unable  to 
connect  the  Dromotheriidae  of  the  Trias,  the  Triconodontidae, 
Amphitheriidae  and  Amblotheriidae  of  the  Jura  with  each 
other,  or  with  any  Cretaceous  or  lower  tertiary  mammals. 
The  serial  relations  of  the  Multituberculatcs,  on  the  other 
hand,  have  been  made  much  clearer  by  the  discovery  of 
the  Laramie  fauna.  Cope  and  Marsh  in  this  country,  and 
Smith  Woodward  in  England,  have  at  last  broken  into  the 
long  barren  Cretaceous.  In  studying  the  accurate  figures  pub- 
lished by  Marsh  and  a  large  collection  of  teeth  recently  made 
for  the  American  Museum  by  Wortman  and  Peterson,  I  find 
that  this  Laramie  fauna  is  widely  separated  from  the  Jurassic 
in  its  general  evolution,  and  as  Gaudry,  Lemoine  and  Cope 
have  observed,  it  approaches  more  nearly  the  basal  Eocene 

87 


jffiii-  ji»jy«lf''TrI» 


""M 


30 


T/Zli   RISE   or   THE  MAMMALIA 


of  the  Pucrco  and  the  Ccrnaysian  of  France.  The  Multitu. 
bcrculates  of  the  Laramie  include  the  riagi.udaeidae,  repre- 
scntcd  by  I'tilodiis,  the  form  with  two  prcnmlars^  and  Mcnt- 
scoessus,  with  two  premolars  and  cresccntic  tubercles.  Meni- 
scotissus  has  a  smaller  fourth  premolar,  and  is  found  to  k.id 
off  to  the  huge  plaj;iaulacid  Polymastodon  of  the  Pucrco. 
The  only  other  Multituberculates  found  are  those  related  to 
Bolodon  of  the  Jurassic  and  Chirox  of  the  Pucrco.  The  other 
mammals  of  the  Laramie  range  from  the  mouse  to  the  opossum 
in  size;  they  have  superior  molars  of  the  simple  tritubercular 
type  —  the  low  cusped  or  bunodont  molar  predominating^  in 
the  upper  jaw,  and  the  tuberculo-scctorial  in  the  lower.  The 
dental  formula  is  mostly  the  typical  p.  4,  m.  3.  Yet,  judging 
by  the  angular  region  of  Mie  jaws,  we  have  here  both  Placentals 
and  Marsupials.  Some  of  the  teeth  remind  us  strongly  of 
those  in  the  Puerco  ;  their  determination,  however,  is  very 
difficult,  for  the  jaws  and  teeth  arc  almost  entirely  isolated. 
From  another  exposure  of  the  Laramie,  Cope  has  recently 
found  the  remarkable  type  Thlaeodon  —  remarkable  because 
it  is  a  highly  specialized  trituberculate  of  typical  dentition 
with  a  jaw  which  bears  resemblance  to  that  of  the  Multitu- 
berculates and  of  Ornithorhynchus.  There  is  no  placental 
angle  nor  strong  marsupial  inflection.  This  raises  the  sup. 
position  that  Thlaeodon  may  be  one  of  the  persistent  trituber- 
culate Monotremes  which  we  are  now  looking  for. 

In  the  Puerco  or  basal  Eocene,  a  very  marked  change  occurs, 
for  the  American  fauna  loses  some  of  its  cosmopolitan  character, 
the  multituberculates  or  monotremes  die  out  and  the  marsu- 
pials are  not  found  at  all ;  in  fact  they  do  not  reappear  in 
North  America  until  the  Miocene. 


Ancient  and  Modern  Placental  Differentiation. 

The  Puerco  is  essentially  an  archaic  fauna  and  is  to  be 
regarded  as  the  climax  of  the  first  period  of  placental  differ- 
entiation, a  culmination  of  the  first  attempts  of  nature  to 
establish  insectivorous,  carnivorous  and  herbivorous  groups. 
These  attempts  began  in  the  Cretaceous,  and  some  of  the 

88 


//.'  NORTH  A.)rERlCA. 


3' 


types   thus  prodiuc-d  died  out   in  tiic   Pucrco,  sonic   in   llic 
Wahsatch  ami  IJi  i(!;;iT  ;    only  a  few   flosh-ratcis  survived  to 
the  Miocene.     It  is  most  important  to  -;rasp  dearly  the  idea 
of  this  functional  radiation  in  all  directions  of  this  old   I'uerco 
fauna,  resulting  in  forms  like  the  modern  inscctivorcs,  rodents, 
bears,  doj^s  and  cats,  monkeys,  sloths,  bunodont  and  seleno- 
dont  ungulates,  and  lophodont  ungulates.     This  was  an  inde- 
pendent radiation  of  placcntals,  like  the  Australian  radiation 
of  marsupials.     What  was  the  cause  of  the  wide-spread  extinc- 
tion of  these  types .'     So  far  as  the  ancient  clawed  types  are 
concerned,  their  teeth  and  feet  seem  to  be  as  fully  adaptive  in 
many  ca.ses  as  those  of  the  later  unguiculates  ;   the  hoofed 
types  were  certainly  inferior  in  tooth  evolution,  for  all  their 
molars  evolved  on  the  triangular  basis  instead  of  the  sexitubcr- 
cular  ;  the  most  sweeping  defect  of  both  the  clawed  and  hoofed 
types,   was  the   apparent    incapacity  for   brain    growth,   their 
bodies  went  on  developing  while  their  brains  stood  still.     Thus 
the  stupid  giant  fauna,  the  Dinocerata,  which  rose  out  of  this 
period,  gave  way  to  the  small  but  large-brained  modern  types. 
It  is  noteworthy  that  the  latest  survivors  of  this  wreck  of  an- 
cicnt  life  were  the  large-brained  Hyaenodons. 

Some  of  the  least  specialized  spurs  of  this  radiation  appear 
to  have  survived  and  become  the  centres  of  the  second  or  mid- 
Tertiary  radiation  from  which  our  modern  fauna  has  evolved. 
Yet  we  have  not  in  a  single  case  succeeded  in  tracing  the 
direct  connection.  To  sum  up,  we  find  on  the  North  American 
continent  evidence  of  the  rise  and  decline  and  disappearance  of 
monotremes  and  marsupials,  and  two  great  periods  of  placental 
radiation,  the  ancient  radiation  beginning  in  the  mesozoic, 
reaching  a  climax  in  the  Puerco  and  unknown  post-Puerco,  and 
sending  its  spurs  into  the  higher  tertiary,  and  the  modern  radia- 
tion reaching  its  climax  in  the  Miocene,  and  sending  down  to 
us  our  existing  types. 

Another  Eocene  centre  was  h  .r  South  America,  which  has 
of  late  dimmed  the  prestige  of  North  America  in  yielding 
strange  forms  of  life.     One  theory  of  this  Patagonian  fauna  is 

89 


32 


THE  RISE   or   HIE  AfAAfAfAUA 


that  it  was  an  independent  centre  of  functional  radiation  like 
the  Pucrco  and  Australian,  lull  of  adaptive  parallels,  but  not 
yielding;  to  Europe  or  America  any  of  their  older  tyijes.     lUit 
Ametihino,  to  whose  energetic   rcsearehes  we  are  chiefly  in- 
debted, believes  that  he  fintls  a  lower  I-'.ocenc  life  zone  —  a  sort 
of  south  polar  centre  —  which    supplied    both    America   and 
ICurope.     The  Puerco  he  believes  is  no  oldi-r  than  the  Santa- 
cruzian  which  in  turn  is  very  much  older  than  the  Parana  and 
Pampean    formations,    which    lUirmeistcr    has    made    so    well 
known.     This  yields  the  Ilomunculus  pata;jjonicus  which  paral- 
lels  Cop^^'s  Anaptomorphus  in  presenting  a  dentition  as  ad- 
vanced in  reduction  as  that  of  man.     Ameghino  finds  here  the 
ancestors  of   the   Macrauchenidac  ;   he  believes  the   Ilomolo- 
dontotheridae   are   the    ancestor?    of    the    Chalicotheriidae  — 
thus  deriving  a  buno-sclenodont  from  a  lophndont  type  ;  the 
Proterotheriidac,   he   believes,   replace   the   Condylarthra   and 
Ilyracothcrium  in  the  ancestry  of  the  horses.     Similarly  the 
Microbiotheriidac  are  the  stem  of  the  creodonts  and  carnivores. 
I  cannot  coincide  with  any  of  these  views.     The  Multitubercu- 
lates  are  far  older  and  widely  different  from  the  Abdcritcs  to 
which  Ameghino  traces   their  ancestry.     I  fully  concur  with 
the  opinion  of  Cope,  Zittel,  Scott  and  others  that  this  fauna  is 
of  somewhat  later  age,   th;it   it  was  directly  connected  with 
Australia  and   somewhat   later  with  North  America,   supply- 
ing us,  as  has   always   been  supposed,  with   our   sloths.      I 
quote  from  a  recent  address  by  Scott  : 

"  The  oldest  mammals  from  South  An  ,'rica  are  those  from  Pata- 
gonia, which  Ameghino  has  referred  tc  the  Eocene,  but  which  arc 
more  probably  Oligocene  or  Miocene.  This  fauna  is  of  extreme 
peculiarity  and  isolation  ;  it  is  made  up  chiefly  of  edentates,  rodents 
and  ungulates  of  those  very  aberrant  types  known  as  IJtopterna  and 
Toxodontia,  which  are  so  widely  different  from  the  hoofed  mammals 
of  the  northern  hemisphere  ;  together  with  some  primitive  forms  of 
primates,  creodonts  and  marsupials.  The  marsupials  are  of  extra- 
ordinary interest,  for  they  comprise  not  only  forms  allied  to  the 
opossums,  but  also  to  recent  Australian  forms  such  as  Thylacinus, 
Dasyurus  and  Hypsiprymnus.  This  is  a  most  unexpected  fact  and 
seems  to  point  unmistakably  to  a  great  southern  circumpolar  con- 
tinent." 


IN  XORT/r  AMERICA, 


II 


The  Pucrco  thus  remains  the  most  extensively  known  and 
productive  lower  eocene  centre  yet  we  have  very  slender 
threads  of  positive  evidence  io  connect  its  fauna  with  the  later 
plarciUal  radiation. 

The   Creodonts  of  Cope  occupy  the  same  relation  to  the 
modern  inscctivores  and  carnivores  that  the  Condylarthra  do 
tr   the  ungulates.     The   American  group   has  been   recently 
enriched  by  the  discoveries  of  VV'ortman,  and  the  literature  by 
the  careful  revision  of  Scott.     This  author  has  divided  them 
into  eight  families,  placing  the  forms  which  most  resend)lc  the 
Inscctivora  in  the  new  family,  Oxyclaeniilae.     These  families 
illustrate  superbly  the  same  law  of  functional  radiation  later 
repeated    in    the   placental   and    marsupial    carnivores.      The 
iMcsonyx  family  presents  some  analogies  to  the  Thylaeines. 
The  modern  bears  arc  parallelled  in  the  Arctocyons,  with  their 
low  tubercular  molars;  VVortman  and  myself,  with  fresh  materi- 
als,  have  recently  added  Anacodon  to  this  family,  a  genus  which 
was  doubtfully  regarded  by  Cope  as  an  ancient  imgulate.     The 
Cats  and  Hyaenas  arc  imitated  in  the  Oxyaenas  and  Ilyaeno- 
dons,   some  of  the   Miocene  forms  of  which  Scott  suggests 
developed  aquatic  habits;  as  above  noted,  some  of  this  family 
acquired  large  brains  and  persisted  well  into  the  Miocene.     A 
still  more  remarkable  likeness  to  the  Cats  is  exhibited  in  the 
Palaeonictis  family,  which,  unlike  the  Hyaenodons,  forms  its 
sectorials  out  of  exactly  the  same  teeth  as  the  true  cats.     The 
first  American  Palaeonictis  was  found  two  years  ago  by  Wort- 
man,  and  this  author  and  myself  have  suggested  that  this  may 
be  the  long-sought  ancestor  of  the  Felidae.     The  Civets  are 
anticipated  in  the  Provivcrridae;  yet  both  Cope  and  Scott,  the 
highest  authorities  on  this  subject,  believe  that  the  dog-like 
Miacidae  alone  formed  the  connecting  link  between  the  Creo- 
donta  and  the  true  Carnivora. 


The  foot  structure  of  the  ancient  Puerco  ungulates  is  still 
only  partly  known.  Cope  has  divided  thes,-  animals  into  the 
Amblypoda  and  Co:.dylarthra.  The  Amblypoda  are  repre- 
sented in  the  Puerco  by  a  large  form  called  Pantolambda,  with 
selenodont   triangular   upper   molars,   and  possibly  by  Pcrip- 


34 


THE  RISE  OF   THE  MAMMALIA 


tychus,  with  bunodont  triangular  molars.     The  Pantolambda 
molars  were,  as  Cope  has  shown,  converted  into  those  of  Cory- 
phodon,  the  great  lophodont  Amblypod  of  the  Wahsatch,  by  a 
process  exactly  analogous  to  that  in  which  the  anterior  half  of 
a    Palaeotherium   molar   was    formed,   that    is,   they  acquired 
outer    and    anterior    crests   but    no    posterior   crests.      This 
Coryphodon  molar  type  was  still  later  converted  into  the  Uin- 
tatherium   type   by  swinging  around  the  outer  crest   into   a 
transverse  crest.     I  have  recently  made  a  careful  study  of  the 
fore  and  hind  feet  of  Coryphodon,  and  have  found  that  while 
the  fore  foot  was  subdigiiigrade  like  that  of  the  -lephant,  the 
hind  foot  was  fully  plantigrade,  the  entire  sole  resting  upon 
the  ground.     The  relation  or  connection  between  the  Bridger 
Dinocerata  and  these  earlier  Amblypoda  is  still  unknown.    The 
Puerco  Periptychus  left  no  descendants.     The  other  ungulates 
of   the  Puerco  were  the  Condylarthra,  the  primitive  Phena- 
codontidae,  the  supposed  ancestors  of   the  Artiodactyls  and 
Pcrissodactyls.     Much  remains  to  be  done  to  clear  up  this 

question. 

Succession  of  the  Perissodactyls. 

In  the  Wahsatch  and  Wind  River  we  find  not  only  the  last 
of  the  Phenacodonts  and  Coryphodonts  and  the  first  of  the 
Dinocerata,  but  the  first  of  the  true  Artiodactyl-.  and  Perisso- 
dactyls. Recent  studies  of  Cope,  Schlosser,  Pavlow,  Filhol 
have  been  directed  to  the  phylogeny  of  the  Perissodactyls  with 
very  different  conclusions.  I  agree  most  closely  with  Schlosser, 
and  have  endeavored  to  show  that  the  molar  teeth  give  us  a 
key  to  their  natural  arrangement  as  shown  in  this  column 


^  Titanotheres. 

{Horses. 
Palaeotheres. 

{Tapirs. 
Lophiodonts. 
(Helaletes). 

/-  Hyracodonts. 
J  Amynodonts. 
I  Rhinoceroses. 


Upon  one  side  the  Titanotheres  pre- 
sent the  seleno-bunofiont  extreme  with 
most  analogies  to  the  Artiodactyla  in 
tooth  structure  and  in  their  truly  Artio- 
dactyl  fore  feet  and  bony  horns.  (If, 
as  Cope  supposes,  the  Diplarthra  form 
a  natural  group,  some  Perissodactyls 
should  certainly  be  more  Artiodactyl 
than  others.)  The  Horses  and  Palaeo- 
theres diverge  from  the  buno-selenodont 


IN  NORTH  AMERICA. 


35 


type  towards  the  Lophodont  ;  they  were  early  separated  in 
foot  structure.  The  Tapirs,  Lophiodonts,  and  Hclaletes  show 
well-marked  transverse  crests  and  incipient  external  crests. 
This  brings  us  to  the  other  Lophodont  extreme,  the  Rhinoceros- 
like forms,  with  complete  transverse  and  external  crests.  There 
are  many  other  minor  characters  which  support  this  as  the 
natural  arrangement  of  the  Perissodactyls.     I  think  it  can  be 


/trctacont  "  Jrtloeane      /">rari,ru  "imfacone 


-  Euprotogonia. 

4th  I'lr.,  1st  M. 

'nttfaconu/e 


Ilyracoth^riuiD. 
4th  P.n.  ist  U. 


tcCartccont    f^ 

fr«"jl.     ma^/j^  mu.jlyi. 


'ijj^Diljh 


Anchitherium.  Coryphodon. 

Homologies  in  the  Horse  and  Coryphodon  Molars  and  Premolars. 

shown  conclusively  that  these  eight  or  nine  scries  diverged 
from  each  other  before  the  Wahsatch,  and  that  all  attempts 
to  derive  them  from  each  otner  in  later  periods  will  break 
down.  They  will  be  found  to  converge  into  the  unknown  Sub- 
Wahsatch  period,  to  stem  forms  as  indicated  by  the  brackets. 

93 


36 


THE   RISE   OF   THE   MAMMALIA 


One  of  the  most  decided  reforms  in  the  matter  of  classifica- 
tion is  the  use  of  the  family  division.     Pre-darwinian  writers 
considered    animals   as   arranged    in    circles  ;     post-darwinian 
writers  all   regard  them  as  in  vertical   lines,  giving  off    side 
branches.     Classification  should  keep  pace  with  phylogeny  in 
palaeontology.     Yet    there    are   two   clcarl>    defined    schools 
of  classification  to-day.     The  one,  led  by   Flower,  Cope,  and 
Lydekker,    practically   adheres    to   the   old    circular    system  ; 
according   to   this,    comprehensive    families    are    formed   out 
of  members  of  different  lines  of  descent  which  happen  to  be 
in   the   same  stage   of    evolution;     lor    example,    among    the 
ungulates,  a  horse  in  the  first  stage  of  its  evolution  is  called 
a  lophiodont  {i.  e.,  it  is  placed  in  the  Lophiodontidae),  in  the 
next  stage  it  is  called  a  palaeothere  {i.e.,  in  the  Palaeotheriidae). 
The  extreme  application  of  this  method  by  Cope  has  led  to  a 
total  misunderstanding  abroad  of  his  real  phylogenetic  views. 
The    other    school,    including    Schlosscr,    Scott,    Zittel,    and 
myself,  adopt  the  vertical  system,  according  to  which  a  horse 
is  called  a  horse,  a  tapir  a  tapir,   a  rhinoceros  a  rhinoceros, 
from  the  moment  when  they  clearly  appear  as  such.     I  have 
attempted  elsewhere  to  show  that  the  circufir  system  is  con- 
fusing,   that    it    ignores   the   divergence   of    structure   which 
resulted   from  thousands  of  years  of    physiological   isolation ; 
that   finally   it   is  only  possible  when  we  define  families  upon 
the  false  system  of  single  characters.     In  England  and  France 
the    adherence    to    the    circular    system   is    largely    due    to 
traditional    reverence     for    the    Lophiodontidae,    which    has 
become  an  omnium  gatherum  for  early  odd-toed  ungulates  — 
just  as  were  the  Pachyderms  of    Cuvier  until  Owen  proved 
that  that   term   had  no   meaning.     To-day,   no   one   can  say 
exactly  what  the  Lophiodon  itself  was  ;  it  appears  to  have  been 
an   aberrant   and   early    extinguished    line.      In   the   vertical 
system  the  great  stages  of  evolution  may  be  indicated  by  sub- 
family divisions,  as  in   the  following  table.     It  is  practically 
the  same  system  as  that  which  Flower  applies  to  the  existing 

mammals. 

All  the  tendency  of  recent  discovery  has  been  to  show  that 
these  lines  are  separate  as  far  back  as  we  can  now  trace  them, 

94 


IN  NORTH  AMERICA. 


11 


that  is,  to  the  Wahsatch  or  Suessonian.  Such  being  the  case, 
we  are  no  more  justified  in  placing  the  ancient  tapirs  and  horses 
in  one  family  (Lophiodontidae)  than  the  modern. 

In  the  matter  of  genera,  opinion  divides  on  different  lines. 
Flower  and  Lydekker  place  all  the  extinct  and  modern  Rhino- 
ceroses   (except    Elasmotherium)    in   one   genus,    while    Cope 


Pliocene. 
Pm  =  M. 


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into  Molars  ;  or  Pm  = 
M. 

White  River  to  Loup 
Fork. 


Middle  and  Upper 
Eocem:. 

Premolars   Simplor  than 
Molars. 

Wahsatch  to  Uinta. 

Basal  Eocene. 
Puerco  to  Wahsatch. 


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Family  Series  converging  into  Condylarthra  or 
Stem  Perissodactyla. 


divides  the  Rhinoceroses  into  a  large  number  of  genera.  Here 
we  are  dealing  not  with  great  separate  lines  of  descent  but  with 
stages  of  evolution  in  the  same  or  a  few  closely  parallel  lines. 
If  we  unite  a  large  number  of  stages  into  one  genus  of  Rh'io- 
ceroses,  to  be  consistent  we  should  do  the  same  with  the  horses 


95 


38 


THE  RISE  OF  THE  MAMMALIA 


and  tapirs.     Nevertheless,  it  is  very  difficult,  if  not  impossible, 
to  agree  as  to  what  shall  constitute  a  generic  stage. 

The  Titanotheres  have  been  traced  by  Cope  back  to  Lanib- 
dotherium  in  the  Wahsatch  ;  in  the  Wind  River  the  true 
Palaeosyops  is  found,  and  in  the  Bridger  this  becomes  the  pre- 
dominant perissodactyl  family,  and  spreads  out  into  a  great 
variety  of  forms,  which  have  recently  been  carefully  described 
by  Earle.  In  the  Washakie  there  are  some  still  larger  forms, 
and  Marsh  has  traced  t'.ie  line  through  the  teeth  of  Diplacodon 
of  the  Uinta  to  the  true  Titanotheres.  Still  the  origin  of  the 
flattened  skull  and  remarkable  anterior  pair  of  horns  has  never 
been  known  ;  Hatcher  reports  species  with  very  small  liorns  in 
the  base  of  the  Titanothcrium  beds  (Lower  Miocene).  Wort- 
man  has  just  reported  to  me  the  brilliant  discovery  of  upper 
Eocene  (Washakie)  Palneosyops  with  a  flattened  skull  and 
rudimentary  horns  just  iippcaring  upon  the  nasal-  !  This 
forms  the  desired  connecting  link. 

The  early  history  of  the  horses,  probably  starting  with  the 
Puerco  Condylarth  luiprotogonia,  and  passing  through  Hyraco- 
therium,  Pach)n()lophus,  Epihippus,  Mesohippus,  is  now  familiar 
enough.     It  is  the  later  history  which  require^elucidation,  and 
is  producing  the  most  unexpected  number  of  parallel  lines  of 
horses,   out   of  one  of  which  only  our  modern  horse  sprang. 
Here  we  are  especially  indebted  to  Cope,  Pavlow,  and  Scott. 
By  general  consent  Hipparion  comes  out  of  its  old  position  in 
tlie  true  line  as  displaying  the  most  extreme  variations  in  the 
crowns  of  the  molar  teeth  in  compensation  for  the  backward 
evolution  of  Us  feet.     Scott  has  been  especially  investigating 
the    upper  Miocene  horses;    I  quote  from  the  MSS.  he  has 
kindly  lent  me,  in  which  he  proposes  to  remove  also  the  classi- 
cal  Anchitherium  of  Cuvier.     He   says  :    "  These  American 
genera,  Mesohippus  and  Miohippus  may  confidently  be  regarded 
as  important  members  of  the  equine  stem,  while  Anchitherium 
(of  Europe)  from  present  information  would  appear  to  belong 
to  an  abortive  side  branch  leading  to  no  permanent  results." 
Scott  has  also  discovered  an  important  intermediate  form  link- 
ing Miohippus  with  Protohippus. 

The  Palaeotheres  have  not  been  found  in  America. 


y6 


^Hh. 


IN  NORTH  AMERICA. 


39 


The  Tapir  line  has  been  traced  by  Cope  anil  myself  back  to 
Systcmodon  of  the  VVahsatch,  and  Isectolophus  of  the  Briilger 
and  Uinta.  These  forms  have  simple  premolars,  but  bear  the 
most  striking  resemblance  to  the  Tapirs  in  the  molars  both 
above  and  below.  All  previous  attempts  to  determine  the 
Miocene  representatives  of  the  Tapirs  have  been  erroneous. 
Wortman  and  Earle  have  just  published  an  account  of  two 
lower  Miocene  species  of  true  Tapirs,  which,  both  in  foot  and 
tooth  structure,  definitely  carry  the  -American  Tapir  line  up  to 
the  middle  Miocene,  where  it  is  again  lost  sight  of.  These 
species  belong  to  the  genus  Protapirus,  which  Filhol  has  found 
in  the  Ol '(jocene  of  France,  thus  adding  an  important  geological 
parallel.  The  Wahsatch  Tapirs  were  a  little  larger  than  the 
Horses  or  Hyracotheres  which  were  about  the  size  of  a  fox, 
and  much  smaller  than  the  ancestral  Titdotheres.  Another 
family  of  snail,  slender  perissodactyls  were  most  nearly  allied 
to  the  Lophiodons  of  Europe  of  any  American  forms.  ' 

These  are  the  Hclaletidae,  distinguished  by  feet  tending  to 
monodactylism,  and  narrow  hoofs  like  those  of  the  deer  ;  even 
in  the  Wahsatch  Heptodon  the  lateral  toes  are  quite  short  and 
raised  off  the  ground.  The  molars,  like  those  of  the  lophiodons 
of  Europe,  are  intermediate  between  those  of  the  Tapir  and 
the  Rhinoceros,  but  both  teeth  and  feet  preclude  our  uniting 
the.sc  forms  either  with  the  Tapirs  or  with  the  Hyrachyus 
family,  as  Cope  has  done.  The  Bridger  successor  is  Helaletes, 
which  Marsh  mistakenly  supposed  was  an  ancestral  Tapir,  and 
the  integrity  of  this  line  is  now  firmly  establishei'  by  the  dis- 
covery of  the  Miocene  Colodon.  This  is  described  by  Marsh 
as  a  successor  of  Helaletes,  and  Wortman  and  Earle  have  just 
published  an  account  of  the  teeth  and  feet,  showing  that 
Colodon  is  widely  separated  from  the  contemporary  Tapirs,  and 
is  the  last  member  of  the  Heptodon-Helaletes  line. 

The  Rhinoceroses  of  America  comprised  the  true  Acera- 
theriinae  and  Diceratheriinae,  and  what  may  be  called  the 
pseudo-rhinoceroses,  the  Hyracodons  and  Amynodons;  all  these 
forms  present  the  true  Rhinoceros  molar  pattern,  but  they 
diverge  most  widely  in  the  structure  of  the  anterior  teeth  and 
of  the  feet.     The  Hyracodons  first  appear  in  the  numerous  and 

97 


1 


40 


THE  RISE  OF  THE  MAMMALIA 


diversified  Hyrachyus  of  the  Bridger,  some  of  which  exhibited 
rudimentary  horns  upon  the  back  part  of  the  nasals  (Colono- 
ceras) ;  they  retained  a  full  set  of  equal-sized  incisors  and 
canines,  and  acquired  a  horse  type  of  skull,  skeleton,  .ind 
locomotion.  Scott  has  well  named  them  the  'cursorial  rhi- 
noceroses.' Colonoceras  prob.ibly  did  not,  as  Marsh  has  sug- 
gested, branch  off  into  Dicerather'um,  for  the  horns  of  this  true 
rhinoceros  are  developed  at  the  ends  of  the  nasals  ;  the  Hyra- 
chyinae  sent  off  as  a  side  branch  the  deer-like  Triplopus  of  the 
Washakie,  and  terminated  in  the  Hyracodons  of  the  lower 
Miocone. 

The  Amynodons,  at  the  time  of  their  discovery  by  Marsh, 
were  naturally  supposed  to  be  the  long-sought  Eocene 
rhinoceroses,  but  I  have  shown  that  no  Amynodon  can  fill  this 
r61e.  Garman  s  discovery  of  the  skull  of  the  remarkable 
Miocene  Metamynodon  tended  to  confirm  my  views,  and  I 
have  now  to  report  the  discovery  of  many  skulls  and  a  nearly 
complete  skeleton  by  tne  American  Museum  Expedition. 
This  proves  that  the  Amynodoniidae  were  remarkable  side 
forms.  In  wide  contrast  with  the  true  rhinoceroses,  the  upper 
and  lower  canines  d^ivelop  into  huge,  partly  recurved  tusks, 
like  those  of  the  boar.  As  in  Elasmotherium,  the  premolars 
become  greatly  reduced,  and  the  molars  tend  to  hypsodontism. 
The  lower  molars  are  long  and  narrow,  like  those  of  the 
anomalous  Cadurcotherium  of  the  Oligocene  of  Europe  —  it 
is  thus  rendered  probable  that  Cadurcotherium  is  not  a  sloth, 
as  Filhol  has  suggested,  but  is  an  aberrant  rhinoceros,  related 
to,  if  not  identical  with,  the  Amynodons.  The  hypsodontism 
in  some  Metamynodoii  teeth  is  accompanied  by  a  partial  loss 
of  enamel.  To  complete  the  aberrant  character  of  this  family, 
we  find  that  it  has  four  equal-sized  and  completely  func- 
tional toes  in  the  forefoot,  like  those  of  the  Titanotheres, 
not  with  the  fifth  toe  reduced  as  in  the  contemporary  Acera- 
theria. 

The  true  Rhinoceroses,  we  remember,  are  distinguished  by 
the  entire  loss  of  upper  canines.  Wortman  has  just  reported 
finding  rudimentary  upper  canines  in  both  the  milk  and 
permanent    dentitions  of    the    older    Miocene    species.     The 


IN  NORTH  AMERICA. 


41 


true  rhinoceroses  suddenly  appear  in  the  lower  Miocene  of 
America  and  Oligocene  of  Europe  ;  we  have  not  yet  traced 
them  back.  In  a  collection  of  lower  Miocene  t.kulls  recently 
obtained  for  the  American  Museum  we  find  that  the  premolars 
are  still  very  simple.  In  fhe  higher  Oreodon  Beds  all  traces 
of  the  superior  canine  are  lost,  and  the  premolars  have 
become  more  like  the  molars.  As  the  origia  of  the 
rhinoceroses  still  remains  a  mystery,  so  their  later  evolution 
needs  clearing  up.  The  American  series  suddenly  terminate 
in  the  huge,  hornless  forms  of  the  upper  Miocene.  I  find 
there  is  still  no  unanimity  of  opinion  in  Europe  as  to  the 
phyletic  relationships  of  the  Miocene,  Pliocene  and  existing 
species. 

Succession  of  t'e  Artiodactyls. . 

The  Eocene  Artiodactyl  phylogeny  is  still  far  behind  that  of 
the  perissodactyls,  but  the  Miocene  and  Pliocene  succession 
has  been  worked  up  with  great  success  and  clearness  by  Cope 
and  Scott.  The  latter  says  in  a  recent  paper  :  "  All  the  great 
groups  of  Artiodactyla  are  seen  to  arise  independently  from 
the  Buno-Selenodonta  which  forms  as  it  were  a  lake,  from 
which  several  streams,  flowing  partly  in  parallel  partly  in 
divergent  directions,  are  deriveci." 

The  Elotheriidae  appear  in  Parahyus  of  the  Bridger  and 
Achaenodon  of  the  Washakie,  and  terminate  in  the  middle 
Miocene  in  the  gigantic  Elotherium  ramosum,  an  animal 
with  a  skull  three  feet  long,  both  the  jaws  and  skull  being 
armed  with  long  branching  processes.  The  true  bunodont 
pigs  and  peccaries  have  not  yet  been  found  lower  than  the 
White  River. 

Scott  has  traced  the  Oreodons  back  to  Protoreodon  of  the 
top  of  the  Eocene.  The  aberrant  Agriochoeridae,  he  believes, 
were  doubtfully  connected  with  the  true  Oreodons  by  a  lower 
Eocene  stem  form.  The  true  Oreodons,  which  exister'  in  great 
herds  in  the  lower  Miocene,  have  been  divided  by  Cope  and 
Scott  into  three  parallel  lines  extending  into  the  Loup  Fork, 
namely,  the  large  Merycochoerus,  the  medium-sized  and  more 
p.imitive  IMerychius  L.nd  the  small,  highly-specialized  Pith- 
ecistes. 


99 


42 


THE  RISE  OF  THE  MAMMALIA 


The  Tragulines  are  represented  by  Leptomcryx,  Hyper- 
tragulus  and  Hypisodus.  Lcptomeryx  is  believed  to  be  a  side 
member  of  the  main  family.  Here  I  may  speak  of  the  recent 
discovery  of  the  characters  of  the  Protoceratidae,  a  new  family 
with  a  remarkable  ensemble  of  characters. 

In  189!  Marsh  described  the  female  skull  of  Protoceras 
with  a  small  pair  of  parietal  protuberances.  The  male  skull 
was  found  in  1892.  It  is  armed  not  only  by  upper  canine 
tusks,  but  by  four  pairs  of  cranial  jirotuberances,  two  of  which 
might  be  dignified  by  the  name  of  osseous  horns  ;  it  thus 
presents  the  armature  of  an  Uintathorium  upon  a  small  scale. 
Besidi  s  parietal  and  two  pairs  of  fr  ntal  protuberances,  there 
are  a  pair  of  most  exceptional  maxillary  plates.  The  fore  foot 
is  like  that  of  Tragulus,  while  the  hind  foot  is  didactyl  like 
the  deer.     We  can  at  present  form  no  idea  of  its  affinities. 

The  oldest  American  Artiodactyl  certainly  known  is  the 
tritubercular  Pantolestes  of  the  VVahsatch.  Cope  believes 
the  line  of  American  Llamas  may  have  sprung  from  this, 
and  have  been  continued  through  Homacodon  of  the  Bridger. 
The  first  undoubted  cameloid  is  Leptotragulus  of  the  Uinta, 
a  comparatively  recent  discovery.  It  has  strikingly  reduced 
feet  for  such  an  early  form.  Poebrotherium«»)f  the  White 
River  and  John  Day  has  quite  the  proportions  of  the  living 
llama  ;  thence  the  line  passes  into  Protolabis  of  the  Deep 
River  and  John  Day.  Scott  believes  that  these  forms  are 
undoubtedly  related  to  both  the  camels  and  llamas,  and 
that  in  the  Loup  Fork,  perhaps  in  the  two  species  of  Proca- 
melus,  the  division  occurs,  P.  angustidens  passing  into  the 
camels,  and  P.  occidentalis  into  the  llamas.  The  Pliocene 
Homocamelus,  Holomeniscus  and  ICschatius,  Scott  believes 
may  represent  a  highly  specialized  side  line  of  camels  ;  while 
Pliauchenia,  still  imperfectly  known,  may  belong  on  the  llama 
side.  The  deer  represented  by  Cosoryx  and  Blastomeryx  are, 
so  far  as  we  know,  not  of  American  origin,  for  they  first  appear 
in  the  Upper  Miocene  at  Loup  P'ork. 


LX  A'ORTII  AMEK/CA. 


The  Ancylopoda, 


43 


The  order  Ancylopoda  Cope  presents  the  most  signal 
exception  to  the  law  of  correlation.  It  is  only  quite  recently 
that  Kilhol,  Forsyth  Major  and  Dcpcret  have  brou^'ht  tof^ether 
the  slotli-like  phalanges  with  the  ungulate  type  of  teeth  of 
the  Chalicotheriidae.  Siiue  1825,  when  Cuvier  described  the 
phalanges  from  ICppelshcini  as  those  of  a  ^ panqolin  gii^nntcsquf,* 
referring  to  their  deep  clefts,  and  1833,  when  Kaup  named  the 
teeth,  these  stnvtures  were  always  considered  distinct.  It  is 
probable  that  Moropus  and  other  sujjposed  Sloths  described 
by  Marsh  from  our  Miocene  also  belong  in  this  cxception^Al 
order.  As  now  restored  by  '  .)1  and  myself,  this  remark- 
able Chalicotherium  had  a  g,  ess  clumsy  than  the  Sloth,  and 
something  between  a  huge  cat  and  a  hoofed  animal;  it  com- 
bined the  skull  of  a  primitive  ungulate  with  the  molars  of  an 
eocene  titanothere,  for  the  premolars  are  simple.  The  limbs, 
wrist  and  ankle  bones  are  chiefly  ungulate  and  peris.sodactyl. 
In  viewing  this  combination  of  characters,  the  first  question 
to  settle  is  which  set  of  characters  is  secondaiy  and  adaptive. 
I  agree  with  Deperet,  as  against  I'Mlhol  who  regards  this  as 
an  aberrant  edentate,  that  the  unguiculate  characters  are  sec- 
ondary; but  I  do  not  believ<_  it  is  very  near  the  perisso- 
dactyla.  It  seems  to  have  sprung  rather  from  the  primitive 
ungulate  stem  before  it  had  parted  with  its  unguiculate  char- 
acters. Perhaps  it  came  off  from  the  VVahsatcii  Mcniscothe- 
rium,  a  member  of  the  Condylarthra,  which  ic  very  closely 
resembles  in  its  skull  and  molar  structure  and  in  its  dental 
curve.  Marsh,  by  the  way,  has  just  added  to  our  knowledge 
of  this  little  Wah.satch  genus  by  describing  its  fore  and  hind 
feet,  which  are  more  primitive  than  tho.se  of  Phenacodus  or 
Hyra.x.  While  the  Creodonta  were  imitating  all  modern  car- 
nivores, is  it  not  possible  that  the  Condylarthra  gave  off  a 
sloth-like  form  for  fossorial  and  semi-arboreal  habits .' 

Last  summer  while  this  problem  was  being  discussed,  we  we'-'- 
brought  to  face  with  the  exact  counterpart  of  Chalicotherium. 
which  may  be  called  a  claivcd  odd-toed  form,  by  the  surprising 
discovery  of  a  hind  foot,  which  represents  a  clawed  even-toed 


•WiPVP 


44 


THE  RISE   OF   THE  MAMMALIA 


animal.  This  was  found  by  the  American  Museum  party  in 
the  Protoceras  beds  of  South  Dakota,  and  has  been  named 
Artionyx.  This  foot  has  a  truly  Artiodactyl  tarsus  and  meta- 
tarsus like  that  of  the  pigs  or  oreodons.  Yet  it  possesses  five 
toes  terminating  in  large  unclcft  claws.  It  has  been  suggested 
by  Wortman  and  myself  that  it  represents  an  Artionychinc 
(even-clawed)  division  and  that  Chalicotherium  represents  a 
Perissonyv-hinc  (odd-clawed)  division  of  the  Ancylopoda  ;  in 
other  words,  that  a  double  parallelism  exists  with  the  Ungu- 
lata.  Another  explanation  may  be  that  these  genera  are  highly 
specialized  Artiodactyla  and  Perissodactyla  respectively;  Scott 
has  made  the  ingenious  suggestion,  tending  to  support  this 
theory,  that  the  Artionyx  foot  is  the  long  unknown  foot  of  the 
aberrant  oreodont  Agriochoerus  of  Leidy.  This  summer  will 
probably  determine  the  truth  of  this  suggestion,  for  two  parties 
are  hunting  in  the  beds  in  which  Agriochoerus  and  Artionyx 

occur. 

Thus  an  immense  number  of  problems  still  await  solution, 
and  demand  the  generous  cooperation  of  European  and  Amer- 
ican specialists  in  the  use  of  similar  methods  of  research,  in 
the  prompt  publication  of  descriptions  and  figures,  and  in  the 
free  use  of  museum  collections.  I  may  be  pard(ftied  for  calling 
general  attention  to  the  service  which  the  palaeontological 
department  of  the  American  Museum  is  trying  to  render  in 
the  immediate  publication  of  stratigraphical  and  descriptive 
tables  of  western  horizons  and  localities. 

The  Factors  of  Evolution. 

A  few  words  in  conclusion  upon  the  impressions  which  a 
study  of  the  rise  of  the  mammalia  gives  as  to  the  factors  of 
organic  evolution.  I  refer  also  to  recent  papers  by  Cope, 
Scott  and  myself. 

The  evolution  of  a  family  like  the  Titanotheres  presents 
an  uninterrupted  march  in  one  direction.  While  apparently 
prosperous  and  attaining  a  great  size,  it  was  really  passing 
into  a  great  corral  of  inadaptation  to  the  grasses  which  were 
introduced  in  the  middle  Miocene.  So  with  other  families 
and  lesser  lines,  extinction  came  in  at  the  end  of  a  term  of 


>iSi>i^... 


■I  i^ui  ,ui...MJW  lyiimiW^-.jLI-J 


/.\'  XOKTJl  A.yfKRfCA. 


45 


development  and  hi};h  specialization.  With  other  families  no 
causes  for  extinction  can  be  assigned,  as  in  the  Ini)pin};  off 
of  the  smaller  Miocene  perissodactyls.  The  point  is  that  ii 
certain  trend  of  develoi)ment  is  taken  leading  to  an  adaptive 
or  inadaptive  final  issue  —  hut  extinction  or  survival  of  the 
fittest  seems  to  exert  little  intluence  tit  route. 

The  changes  en  route  lead  us  to  believe  cither  in  predes- 
tination—  a  kind  of  internal  perfecting  tendency,  or  in  kineto- 
genesis.  I'or  the  trend  of  evolution  is  not  tlie  happy  resultant 
of  many  trials,  but  is  heralded  in  structures  of  the  same  form 
all  the  world  over  and  in  age  after  age,  by  similar  minute 
changes  advancing  irresistil)ly  from  inutility  to  utility.  It 
i.s  an  absolutely  definite  and  lawful  progression.  The  infinite 
number  of  contemporary  developing,  degenerating  and  station- 
ary characters  preclude  the  possibility  of  fortuity.  There  is 
some  law  introc'-Jng  and  regulating  each  of  these  variations, 
as  in  the  variations  of  imlividual  growth. 

The  limits  of  variation  seem  to  lie  partly  in  what  I  have 
called  the  'potential  of  evolution.'  As  the  oiisperni  or  fertilized 
ovum  is  the  potential  adult,  so  the  ICocene  mola'"  is  the  poten- 
tial Miocene  molar.  We  have  seen  that  the  variations  of  the 
horse  and  rhinoceros  molars,  apparently  so  diverse,  are  n.-ally 
uniform,  —  is  not  this  evidence  that  the  stem  peris.sodactyl  had 
these  variations //?/tv///rt//)',  waiting  to  be  called  forth  by  certain 
stimuli }  This  capacity  of  similar  development  under  certain 
stimuli  is  part  of  the  law  of  mammalian  evolution,  but  this 
does  not  decide  the  crucial  point  whether  the  stimulus  is  spon- 
taneous in  the  germ  or  inherited  from  the  parent.  I  incline 
to  the  latter  opinion. 

Columbia  College,  August  3,  1893. 


10] 


